Position-dependent intra-inter prediction combination in video coding

ABSTRACT

A device for coding video data includes a processor configured to generate an inter-prediction block and an intra-prediction block for a current block of video data; for each sample of a prediction block to be generated: determine a first weight for the sample according to a position of the sample in the prediction block; determine a second weight for the sample according to the position of the sample in the prediction block; apply the first weight to a sample at the position in the inter-prediction block to generate a weighted inter-prediction sample; apply the second weight to a sample at the position in the intra-prediction block to generate a weighted intra-prediction sample; and calculate a value for the sample at the position in the prediction block using the weighted inter-prediction sample and the weighted intra-prediction sample; and code the current block using the prediction block.

This application is a divisional of U.S. patent application Ser. No.16/684,379, filed Nov. 14, 2019, which claims the benefit of U.S.Provisional Application No. 62/768,655, filed Nov. 16, 2018, the entirecontents of each of which are hereby incorporated by reference.

TECHNICAL FIELD

This disclosure relates to video coding.

BACKGROUND

Digital video capabilities can be incorporated into a wide range ofdevices, including digital televisions, digital direct broadcastsystems, wireless broadcast systems, personal digital assistants (PDAs),laptop or desktop computers, tablet computers, e-book readers, digitalcameras, digital recording devices, digital media players, video gamingdevices, video game consoles, cellular or satellite radio telephones,smart phones, video teleconferencing devices, video streaming devices,and the like. Digital video devices implement video compressiontechniques, such as those described in the standards defined by ITU-TH.261, ISO/IEC MPEG-1 Visual, ITU-T H.262 or ISO/IEC MPEG-2 Visual,ITU-T H.263, ISO/IEC MPEG-4 Visual, ITU-T H.264 (also known as ISO/IECMPEG-4 AVC), including its Scalable Video Coding (SVC) and MultiviewVideo Coding (MVC) extensions and ITU-T H.265 (also known as ISO/IECMPEG-4 HEVC) with its extensions, MPEG-2, MPEG-4, ITU-T H.263, ITU-TH.264/MPEG-4, Part 10, Advanced Video Coding (AVC), the High EfficiencyVideo Coding (HEVC) standard, and extensions of such standards. Duringthe April 2018 meeting of the Joint Video Experts Team (WET), theVersatile Video Coding (VVC) standardization activity (also known asITU-T H.266) commenced, with the evaluation of the video compressiontechnologies submitted in response to the Call for Proposals. The videodevices may transmit, receive, encode, decode, and/or store digitalvideo information more efficiently by implementing such video codingtechniques.

Video coding techniques include spatial (intra-picture) predictionand/or temporal (inter-picture) prediction to reduce or removeredundancy inherent in video sequences. For block-based video coding, avideo slice (e.g., a video frame or a portion of a video frame) may bepartitioned into video blocks, such as coding tree blocks and codingblocks. Spatial or temporal prediction results in a prediction block fora block to be coded. Residual data represents pixel differences betweenthe original block to be coded and the prediction block. For furthercompression, the residual data may be transformed from the pixel domainto a transform domain, resulting in residual transform coefficients,which then may be quantized.

SUMMARY

In general, this disclosure describes techniques related to combiningintra- and inter-prediction blocks to form a prediction block for acurrent block of video data. In particular, this disclosure describestechniques for weighting samples of an intra-prediction block and aninter-prediction block during the combination, where the weights may bedetermined as a function of a position of the samples. That is, for twosamples at a co-located position in the inter- and intra-predictionblocks, a video coder (encoder or decoder) may determine weights to beapplied based on the position. Thus, the weights may be said to beposition-dependent. Different positions within the intra- andinter-prediction blocks may have different respective weights. The videocoder may apply these weights to the respective samples of the intra-and inter-prediction blocks, then combine the samples to generate avalue for the prediction block generated from the intra- andinter-prediction blocks for the current block. The video coder may thencode (encode or decode) the block using the prediction block.

In one example, a method of coding (encoding or decoding) video dataincludes generating an inter-prediction block for a current block ofvideo data; generating an intra-prediction block for the current block;generating a prediction block for the current block, comprising, foreach sample of the prediction block: determining a first weight for thesample according to a position of the sample in the prediction block;determining a second weight for the sample according to the position ofthe sample in the prediction block; applying the first weight to asample at the position in the inter-prediction block to generate aweighted inter-prediction sample; applying the second weight to a sampleat the position in the intra-prediction block to generate a weightedintra-prediction sample; and calculating a value for the sample at theposition in the prediction block using the weighted inter-predictionsample and the weighted intra-prediction sample; and coding the currentblock using the prediction block.

In another example, a device for coding (encoding or decoding) videodata includes a memory configured to store video data; and one or moreprocessors implemented in circuitry and configured to: generate aninter-prediction block for a current block of the video data; generatean intra-prediction block for the current block; generate a predictionblock for the current block, wherein to generate the prediction block,the one or more processors are configured to, for each sample of theprediction block: determine a first weight for the sample according to aposition of the sample in the prediction block; determine a secondweight for the sample according to the position of the sample in theprediction block; apply the first weight to a sample at the position inthe inter-prediction block to generate a weighted inter-predictionsample; apply the second weight to a sample at the position in theintra-prediction block to generate a weighted intra-prediction sample;and calculate a value for the sample at the position in the predictionblock using the weighted inter-prediction sample and the weightedintra-prediction sample; and code the current block using the predictionblock.

In another example, a device for coding (encoding or decoding) videodata includes means for generating an inter-prediction block for acurrent block of video data; means for generating an intra-predictionblock for the current block; means for generating each sample of theprediction block for the current block, comprising: means fordetermining a first weight for the sample according to a position of thesample in the prediction block; means for determining a second weightfor the sample according to the position of the sample in the predictionblock; means for applying the first weight to a sample at the positionin the inter-prediction block to generate a weighted inter-predictionsample; means for applying the second weight to a sample at the positionin the intra-prediction block to generate a weighted intra-predictionsample; and means for calculating a value for the sample at the positionin the prediction block using the weighted inter-prediction sample andthe weighted intra-prediction sample; and means for coding the currentblock using the prediction block.

In another example, a computer-readable storage medium has storedthereon instructions that, when executed, cause a processor to: generatean inter-prediction block for a current block of video data; generate anintra-prediction block for the current block; generate a predictionblock for the current block, comprising instructions that cause theprocessor to, for each sample of the prediction block: determine a firstweight for the sample according to a position of the sample in theprediction block; determine a second weight for the sample according tothe position of the sample in the prediction block; apply the firstweight to a sample at the position in the inter-prediction block togenerate a weighted inter-prediction sample; apply the second weight toa sample at the position in the intra-prediction block to generate aweighted intra-prediction sample; and calculate a value for the sampleat the position in the prediction block using the weightedinter-prediction sample and the weighted intra-prediction sample; andcode the current block using the prediction block.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an example video encoding anddecoding system that may perform one or more techniques described inthis disclosure.

FIG. 2 is a diagram illustrating examples of DC mode position-dependentprediction combination (PDPC) weights for (0, 0) and (1, 0) positionsinside one 4×4 block.

FIG. 3 is a diagram illustrating example intra prediction modes.

FIGS. 4A-4D are conceptual diagrams illustrating PDPC definitions.

FIG. 5 is a diagram illustrating example intra prediction modes.

FIG. 6 is a block diagram illustrating an example of an 8×4 rectangularblock.

FIGS. 7A-7C are block diagrams providing illustrations of mode mappingprocesses for modes outside of diagonal direction ranges.

FIG. 8 is a conceptual diagram illustrating wide angles that are adoptedin VTM2.

FIG. 9 is a conceptual diagram illustrating wider angles that areadopted in VTM3.

FIG. 10 illustrates aspects of triangular motion compensated prediction.

FIG. 11 illustrates aspects of the adaptive weighting process.

FIGS. 12A and 12B are conceptual diagrams illustrating an example of acombination for two samples.

FIGS. 13A-13D are conceptual diagrams illustrating examples of howreference samples may change by position of a sample.

FIG. 14 is a block diagram illustrating an example video encoder thatmay implement one or more techniques described in this disclosure.

FIG. 15 is a block diagram illustrating an example video decoder thatmay implement one or more techniques described in this disclosure.

FIG. 16 is a flowchart illustrating an example method of encoding videodata according to the techniques of this disclosure.

FIG. 17 is a flowchart illustrating an example method of decoding videodata according to the techniques of this disclosure.

DETAILED DESCRIPTION

A video coder (e.g., a video encoder or a video decoder) may use intraprediction to generate a prediction block for a current block of acurrent picture. In general, when using intra prediction to generate aprediction block, the video coder determines a set of reference samplesin a column left of the current block in the current picture and/or in arow above the current block in the current picture. The video coder maythen use the reference samples to determine values of samples in theprediction block.

In High Efficiency Video Coding (HEVC) and other video coding standards,the video coder performs intra reference smoothing, also known asmode-dependent intra smoothing (MDIS). When the video coder performsintra reference smoothing or MDIS, the video coder applies a filter tothe reference samples prior to using the reference samples to determinepredicted values of samples in the prediction block. For instance, thevideo coder may apply a 2-tap linear filter or a 3-tap (1,2,1)/4 filterto the reference samples. In the filter description above, the ‘/4’denotes normalization by dividing results by 4. Typically, performingintra reference smoothing improves prediction accuracy, especially whenthe current block represents a smoothly varying gradient.

While MDIS may improve prediction accuracy in many situations, there areother situations in which it may be beneficial to use the unfilteredreference samples. Position-dependent prediction combination (PDPC) is ascheme that has been devised to address these issues and improve intraprediction. In the PDPC scheme, a video coder determines a value of aprediction block sample based on the filtered reference samples,unfiltered reference samples, and the position of the prediction blocksample within the prediction block. Use of the PDPC scheme may beassociated with coding efficiency gains. For instance, the same amountof video data may be encoded using fewer bits.

Block-based intra prediction is part of video standards such AVC, HEVC,VVC, etc. Typically, lines of reference samples from adjacentreconstructed blocks are used for predicting samples within the currentblock. One or multiple lines of samples may be used for prediction. Thereference samples are employed by typical intra prediction modes such asDC, planar, and angular/directional modes.

PDPC was proposed in ITU-T SG16/Q6 Doc. COM16-C1046, “Position Dependentintra Prediction Combination (PDPC)” and further simplified in “EE1related: Simplification and extension of PDPC”, 8th JVET Meeting, Macau,October 2018, JVET-H0057 by X. Zhao, V. Seregin, A. Said, and M.Karczewicz. In “Description of SDR, HDR and 360° video coding technologyproposal by Qualcomm,” 10^(th) JVET Meeting, San Diego, Calif., USA,April 2018, JVET-J0021 by M. Karczewicz et al, which is a submission toJVET's call for proposals, PDPC is applied to planar, DC, horizontal andvertical modes without signaling as summarized in the following. In“Extension of Simplified PDPC to Diagonal Intra Modes,” 10^(th) JVETMeeting, San Diego, Calif., USA, April 2018, JVET-J0069 by G. Van derAuwera, V. Seregin, A. Said, M. Karczewicz, PDPC was further extended todiagonal directional modes and modes adjacent to diagonal directionalmodes.

This disclosure describes techniques and system configurations that mayaddress the following potential issues. First, a potential problem isthat PDPC is applied before the intra-inter blending step, which mayadversely affect coding efficiency and implementation complexity.Second, in case of triangular motion compensated prediction, the twotriangular prediction units are only applied to a motion-compensated orinter-predicted CU. Blending of one intra and one inter triangularprediction unit is not supported. There exist ambiguities with respectto how PDPC together with blending is applied in this case. Third, theMDIS filtering may be applied to the reference samples for intraprediction before intra-inter blending, which may adversely affectcoding efficiency and implementation complexity. The details of one ormore aspects of the disclosure are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages of the techniques described in this disclosure will beapparent from the description, drawings, and the claims.

FIG. 1 is a block diagram illustrating an example video encoding anddecoding system 100 that may perform the techniques of this disclosure.The techniques of this disclosure are generally directed to coding(encoding and/or decoding) video data. In general, video data includesany data for processing a video. Thus, video data may include raw,uncoded video, encoded video, decoded (e.g., reconstructed) video, andvideo metadata, such as signaling data.

As shown in FIG. 1 , system 100 includes a source device 102 thatprovides encoded video data to be decoded and displayed by a destinationdevice 116, in this example. In particular, source device 102 providesthe video data to destination device 116 via a computer-readable medium110. Source device 102 and destination device 116 may be any of a widerange of devices, including desktop computers, notebook (i.e., laptop)computers, tablet computers, set-top boxes, telephone handsets such assmartphones, televisions, cameras, display devices, digital mediaplayers, video gaming consoles, video streaming device, or the like. Insome cases, source device 102 and destination device 116 may be equippedfor wireless communication, and thus may be referred to as wirelesscommunication devices.

In the example of FIG. 1 , source device 102 includes video source 104,memory 106, video encoder 200, and output interface 108. Destinationdevice 116 includes input interface 122, video decoder 300, memory 120,and display device 118. In accordance with this disclosure, videoencoder 200 of source device 102 and video decoder 300 of destinationdevice 116 may be configured to apply the techniques for cross-componentprediction. Thus, source device 102 represents an example of a videoencoding device, while destination device 116 represents an example of avideo decoding device. In other examples, a source device and adestination device may include other components or arrangements. Forexample, source device 102 may receive video data from an external videosource, such as an external camera. Likewise, destination device 116 mayinterface with an external display device, rather than including anintegrated display device.

System 100 as shown in FIG. 1 is merely one example. In general, anydigital video encoding and/or decoding device may perform techniques forcross-component prediction. Source device 102 and destination device 116are merely examples of such coding devices in which source device 102generates coded video data for transmission to destination device 116.This disclosure refers to a “coding” device as a device that performscoding (encoding and/or decoding) of data. Thus, video encoder 200 andvideo decoder 300 represent examples of coding devices, in particular, avideo encoder and a video decoder, respectively. In some examples,source device 102 and destination device 116 may operate in asubstantially symmetrical manner such that each of source device 102 anddestination device 116 include video encoding and decoding components.Hence, system 100 may support one-way or two-way video transmissionbetween video source device 102 and destination device 116, e.g., forvideo streaming, video playback, video broadcasting, or video telephony.

In general, video source 104 represents a source of video data (i.e.,raw, uncoded video data) and provides a sequential series of pictures(also referred to as “frames”) of the video data to video encoder 200,which encodes data for the pictures. Video source 104 of source device102 may include a video capture device, such as a video camera, a videoarchive containing previously captured raw video, and/or a video feedinterface to receive video from a video content provider. As a furtheralternative, video source 104 may generate computer graphics-based dataas the source video, or a combination of live video, archived video, andcomputer-generated video. In each case, video encoder 200 encodes thecaptured, pre-captured, or computer-generated video data. Video encoder200 may rearrange the pictures from the received order (sometimesreferred to as “display order”) into a coding order for coding. Videoencoder 200 may generate a bitstream including encoded video data.Source device 102 may then output the encoded video data via outputinterface 108 onto computer-readable medium 110 for reception and/orretrieval by, e.g., input interface 122 of destination device 116.

Memory 106 of source device 102 and memory 120 of destination device 116represent general purpose memories. In some examples, memories 106, 120may store raw video data, e.g., raw video from video source 104 and raw,decoded video data from video decoder 300. Additionally oralternatively, memories 106, 120 may store software instructionsexecutable by, e.g., video encoder 200 and video decoder 300,respectively. Although shown separately from video encoder 200 and videodecoder 300 in this example, it should be understood that video encoder200 and video decoder 300 may also include internal memories forfunctionally similar or equivalent purposes. Furthermore, memories 106,120 may store encoded video data, e.g., output from video encoder 200and input to video decoder 300. In some examples, portions of memories106, 120 may be allocated as one or more video buffers, e.g., to storeraw, decoded, and/or encoded video data.

Computer-readable medium 110 may represent any type of medium or devicecapable of transporting the encoded video data from source device 102 todestination device 116. In one example, computer-readable medium 110represents a communication medium to enable source device 102 totransmit encoded video data directly to destination device 116 inreal-time, e.g., via a radio frequency network or computer-basednetwork. Output interface 108 may modulate a transmission signalincluding the encoded video data, and input interface 122 may demodulatethe received transmission signal, according to a communication standard,such as a wireless communication protocol. The communication medium mayinclude one or both of a wireless or wired communication medium, such asa radio frequency (RF) spectrum or one or more physical transmissionlines. The communication medium may form part of a packet-based network,such as a local area network, a wide-area network, or a global networksuch as the Internet. The communication medium may include routers,switches, base stations, or any other equipment that may be useful tofacilitate communication from source device 102 to destination device116.

In some examples, source device 102 may output encoded data from outputinterface 108 to storage device 112. Similarly, destination device 116may access encoded data from storage device 112 via input interface 122.Storage device 112 may include any of a variety of distributed orlocally accessed data storage media such as a hard drive, Blu-ray discs,DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or anyother suitable digital storage media for storing encoded video data.

In some examples, source device 102 may output encoded video data tofile server 114 or another intermediate storage device that may storethe encoded video generated by source device 102. Destination device 116may access stored video data from file server 114 via streaming ordownload. File server 114 may be any type of server device capable ofstoring encoded video data and transmitting that encoded video data tothe destination device 116. File server 114 may represent a web server(e.g., for a website), a File Transfer Protocol (FTP) server, a contentdelivery network device, or a network attached storage (NAS) device.Destination device 116 may access encoded video data from file server114 through any standard data connection, including an Internetconnection. This may include a wireless channel (e.g., a Wi-Ficonnection), a wired connection (e.g., digital subscriber line (DSL),cable modem, etc.), or a combination of both that is suitable foraccessing encoded video data stored on file server 114. File server 114and input interface 122 may be configured to operate according to astreaming transmission protocol, a download transmission protocol, or acombination thereof.

Output interface 108 and input interface 122 may represent wirelesstransmitters/receivers, modems, wired networking components (e.g.,Ethernet cards), wireless communication components that operateaccording to any of a variety of IEEE 802.11 standards, or otherphysical components. In examples where output interface 108 and inputinterface 122 include wireless components, output interface 108 andinput interface 122 may be configured to transfer data, such as encodedvideo data, according to a cellular communication standard, such as 4G,4G-LTE (Long-Term Evolution), LTE Advanced, 5G, or the like. In someexamples where output interface 108 includes a wireless transmitter,output interface 108 and input interface 122 may be configured totransfer data, such as encoded video data, according to other wirelessstandards, such as an IEEE 802.11 specification, an IEEE 802.15specification (e.g., ZigBee™), a Bluetooth™ standard, or the like. Insome examples, source device 102 and/or destination device 116 mayinclude respective system-on-a-chip (SoC) devices. For example, sourcedevice 102 may include an SoC device to perform the functionalityattributed to video encoder 200 and/or output interface 108, anddestination device 116 may include an SoC device to perform thefunctionality attributed to video decoder 300 and/or input interface122.

The techniques of this disclosure may be applied to video coding insupport of any of a variety of multimedia applications, such asover-the-air television broadcasts, cable television transmissions,satellite television transmissions, Internet streaming videotransmissions, such as dynamic adaptive streaming over HTTP (DASH),digital video that is encoded onto a data storage medium, decoding ofdigital video stored on a data storage medium, or other applications.

Input interface 122 of destination device 116 receives an encoded videobitstream from computer-readable medium 110 (e.g., storage device 112,file server 114, or the like). The encoded video bitstream ofcomputer-readable medium 110 may include signaling information definedby video encoder 200, which is also used by video decoder 300, such assyntax elements having values that describe characteristics and/orprocessing of video blocks or other coded units (e.g., slices, pictures,groups of pictures, sequences, or the like). Display device 118 displaysdecoded pictures of the decoded video data to a user. Display device 118may represent any of a variety of display devices such as a cathode raytube (CRT), a liquid crystal display (LCD), a plasma display, an organiclight emitting diode (OLED) display, or another type of display device.

Although not shown in FIG. 1 , in some examples, video encoder 200 andvideo decoder 300 may each be integrated with an audio encoder and/oraudio decoder, and may include appropriate MUX-DEMUX units, or otherhardware and/or software, to handle multiplexed streams including bothaudio and video in a common data stream. If applicable, MUX-DEMUX unitsmay conform to the ITU H.223 multiplexer protocol, or other protocolssuch as the user datagram protocol (UDP).

Video encoder 200 and video decoder 300 each may be implemented as anyof a variety of suitable encoder and/or decoder circuitry (e.g.,processing circuitry), such as one or more microprocessors, digitalsignal processors (DSPs), application specific integrated circuits(ASICs), field programmable gate arrays (FPGAs), discrete logic, fixedfunction circuitry, programmable processing circuitry, hardware,firmware, hardware implementing software, or any combinations thereof.When the techniques are implemented partially in software, a device maystore instructions for the software in a suitable, non-transitorycomputer-readable medium and execute the instructions in hardware usingone or more processors to perform the techniques of this disclosure.Each of video encoder 200 and video decoder 300 may be included in oneor more encoders or decoders, either of which may be integrated as partof a combined encoder/decoder (CODEC) in a respective device. A deviceincluding video encoder 200 and/or video decoder 300 may include anintegrated circuit, a microprocessor, and/or a wireless communicationdevice, such as a cellular telephone.

Video encoder 200 and video decoder 300 may operate according to a videocoding standard, such as ITU-T H.265, also referred to as HighEfficiency Video Coding (HEVC) or extensions thereto, such as themulti-view and/or scalable video coding extensions. Alternatively, videoencoder 200 and video decoder 300 may operate according to otherproprietary or industry standards, such as the Joint Exploration TestModel (JEM). The techniques of this disclosure, however, are not limitedto any particular coding standard.

In general, video encoder 200 and video decoder 300 may performblock-based coding of pictures. The term “block” generally refers to astructure including data to be processed (e.g., encoded, decoded, orotherwise used in the encoding and/or decoding process). For example, ablock may include a two-dimensional matrix of samples of luminanceand/or chrominance data. In general, video encoder 200 and video decoder300 may code video data represented in a YUV (e.g., Y, Cb, Cr) format.That is, rather than coding red, green, and blue (RGB) data for samplesof a picture, video encoder 200 and video decoder 300 may code luminanceand chrominance components, where the chrominance components may includeboth red hue and blue hue chrominance components. In some examples,video encoder 200 converts received RGB formatted data to a YUVrepresentation prior to encoding, and video decoder 300 converts the YUVrepresentation to the RGB format. Alternatively, pre- andpost-processing units (not shown) may perform these conversions.

This disclosure may generally refer to coding (e.g., encoding anddecoding) of pictures to include the process of encoding or decodingdata of the picture. Similarly, this disclosure may refer to coding ofblocks of a picture to include the process of encoding or decoding datafor the blocks, e.g., prediction and/or residual coding. An encodedvideo bitstream generally includes a series of values for syntaxelements representative of coding decisions (e.g., coding modes) andpartitioning of pictures into blocks. Thus, references to coding apicture or a block should generally be understood as coding values forsyntax elements forming the picture or block.

HEVC defines various blocks, including coding units (CUs), predictionunits (PUs), and transform units (TUs). According to HEVC, a video coder(such as video encoder 200) partitions a coding tree unit (CTU) into CUsaccording to a quadtree structure. That is, the video coder partitionsCTUs and CUs into four equal, non-overlapping squares, and each node ofthe quadtree has either zero or four child nodes. Nodes without childnodes may be referred to as “leaf nodes,” and CUs of such leaf nodes mayinclude one or more PUs and/or one or more TUs. The video coder mayfurther partition PUs and TUs. For example, in HEVC, a residual quadtree(RQT) represents partitioning of TUs. In HEVC, PUs representinter-prediction data, while TUs represent residual data. CUs that areintra-predicted include intra-prediction information, such as anintra-mode indication.

As another example, video encoder 200 and video decoder 300 may beconfigured to operate according to JEM or VVC. According to JEM or VVC,a video coder (such as video encoder 200) partitions a picture into aplurality of coding tree units (CTUs). Video encoder 200 may partition aCTU according to a tree structure, such as a quadtree-binary tree (QTBT)structure or Multi-Type Tree (MTT) structure. The QTBT structure removesthe concepts of multiple partition types, such as the separation betweenCUs, PUs, and TUs of HEVC. A QTBT structure includes two levels: a firstlevel partitioned according to quadtree partitioning, and a second levelpartitioned according to binary tree partitioning. A root node of theQTBT structure corresponds to a CTU. Leaf nodes of the binary treescorrespond to coding units (CUs).

In an MTT partitioning structure, blocks may be partitioned using aquadtree (QT) partition, a binary tree (BT) partition, and one or moretypes of triple tree (TT) (also called ternary tree (TT)) partitions. Atriple or ternary tree partition is a partition where a block is splitinto three sub-blocks. In some examples, a triple or ternary treepartition divides a block into three sub-blocks without dividing theoriginal block through the center. The partitioning types in MTT (e.g.,QT, BT, and TT), may be symmetrical or asymmetrical.

In some examples, video encoder 200 and video decoder 300 may use asingle QTBT or MTT structure to represent each of the luminance andchrominance components, while in other examples, video encoder 200 andvideo decoder 300 may use two or more QTBT or MTT structures, such asone QTBT/MTT structure for the luminance component and another QTBT/MTTstructure for both chrominance components (or two QTBT/MTT structuresfor respective chrominance components).

Video encoder 200 and video decoder 300 may be configured to usequadtree partitioning per HEVC, QTBT partitioning, MTT partitioning, orother partitioning structures. For purposes of explanation, thedescription of the techniques of this disclosure is presented withrespect to QTBT partitioning. However, it should be understood that thetechniques of this disclosure may also be applied to video codersconfigured to use quadtree partitioning, or other types of partitioningas well.

The blocks (e.g., CTUs or CUs) may be grouped in various ways in apicture. As one example, a brick may refer to a rectangular region ofCTU rows within a particular tile in a picture. A tile may be arectangular region of CTUs within a particular tile column and aparticular tile row in a picture. A tile column refers to a rectangularregion of CTUs having a height equal to the height of the picture and awidth specified by syntax elements (e.g., such as in a picture parameterset). A tile row refers to a rectangular region of CTUs having a heightspecified by syntax elements (e.g., such as in a picture parameter set)and a width equal to the width of the picture.

In some examples, a tile may be partitioned into multiple bricks, eachof which may include one or more CTU rows within the tile. A tile thatis not partitioned into multiple bricks may also be referred to as abrick. However, a brick that is a true subset of a tile may not bereferred to as a tile.

The bricks in a picture may also be arranged in a slice. A slice may bean integer number of bricks of a picture that may be exclusivelycontained in a single network abstraction layer (NAL) unit. In someexamples, a slice includes either a number of complete tiles or only aconsecutive sequence of complete bricks of one tile.

This disclosure may use “N×N” and “N by N” interchangeably to refer tothe sample dimensions of a block (such as a CU or other video block) interms of vertical and horizontal dimensions, e.g., 16×16 samples or 16by 16 samples. In general, a 16×16 CU will have 16 samples in a verticaldirection (y=16) and 16 samples in a horizontal direction (x=16).Likewise, an N×N CU generally has N samples in a vertical direction andN samples in a horizontal direction, where N represents a nonnegativeinteger value. The samples in a CU may be arranged in rows and columns.Moreover, CUs need not necessarily have the same number of samples inthe horizontal direction as in the vertical direction. For example, CUsmay include N×M samples, where M is not necessarily equal to N.

Video encoder 200 encodes video data for CUs representing predictionand/or residual information, and other information. The predictioninformation indicates how the CU is to be predicted in order to form aprediction block for the CU. The residual information generallyrepresents sample-by-sample differences between samples of the CU priorto encoding and the prediction block.

To predict a CU, video encoder 200 may generally form a prediction blockfor the CU through inter-prediction or intra-prediction.Inter-prediction generally refers to predicting the CU from data of apreviously coded picture, whereas intra-prediction generally refers topredicting the CU from previously coded data of the same picture. Toperform inter-prediction, video encoder 200 may generate the predictionblock using one or more motion vectors. Video encoder 200 may generallyperform a motion search to identify a reference block that closelymatches the CU, e.g., in terms of differences between the CU and thereference block. Video encoder 200 may calculate a difference metricusing a sum of absolute difference (SAD), sum of squared differences(SSD), mean absolute difference (MAD), mean squared differences (MSD),or other such difference calculations to determine whether a referenceblock closely matches the current CU. In some examples, video encoder200 may predict the current CU using uni-directional prediction orbi-directional prediction.

JEM also provides an affine motion compensation mode, which may beconsidered an inter-prediction mode. In affine motion compensation mode,video encoder 200 may determine two or more motion vectors thatrepresent non-translational motion, such as zoom in or out, rotation,perspective motion, or other irregular motion types.

To perform intra-prediction, video encoder 200 may select anintra-prediction mode to generate the prediction block. JEM providessixty-seven intra-prediction modes, including various directional modes,as well as planar mode and DC mode. In general, video encoder 200selects an intra-prediction mode that describes neighboring samples to acurrent block (e.g., a block of a CU) from which to predict samples ofthe current block. Such samples may generally be above, above and to theleft, or to the left of the current block in the same picture as thecurrent block, assuming video encoder 200 codes CTUs and CUs in rasterscan order (left to right, top to bottom).

Video encoder 200 encodes data representing the prediction mode for acurrent block. For example, for inter-prediction modes, video encoder200 may encode data representing which of the various availableinter-prediction modes is used, as well as motion information for thecorresponding mode. For uni-directional or bi-directionalinter-prediction, for example, video encoder 200 may encode motionvectors using advanced motion vector prediction (AMVP) or merge mode.Video encoder 200 may use similar modes to encode motion vectors foraffine motion compensation mode.

Following prediction, such as intra-prediction or inter-prediction of ablock, video encoder 200 may calculate residual data for the block. Theresidual data, such as a residual block, represents sample by sampledifferences between the block and a prediction block for the block,formed using the corresponding prediction mode. Video encoder 200 mayapply one or more transforms to the residual block, to producetransformed data in a transform domain instead of the sample domain. Forexample, video encoder 200 may apply a discrete cosine transform (DCT),an integer transform, a wavelet transform, or a conceptually similartransform to residual video data. Additionally, video encoder 200 mayapply a secondary transform following the first transform, such as amode-dependent non-separable secondary transform (MDNSST), a signaldependent transform, a Karhunen-Loeve transform (KLT), or the like.Video encoder 200 produces transform coefficients following applicationof the one or more transforms.

As noted above, following any transforms to produce transformcoefficients, video encoder 200 may perform quantization of thetransform coefficients. Quantization generally refers to a process inwhich transform coefficients are quantized to possibly reduce the amountof data used to represent the coefficients, providing furthercompression. By performing the quantization process, video encoder 200may reduce the bit depth associated with some or all of thecoefficients. For example, video encoder 200 may round an n-bit valuedown to an m-bit value during quantization, where n is greater than m.In some examples, to perform quantization, video encoder 200 may performa bitwise right-shift of the value to be quantized.

Following quantization, video encoder 200 may scan the transformcoefficients, producing a one-dimensional vector from thetwo-dimensional matrix including the quantized transform coefficients.The scan may be designed to place higher energy (and therefore lowerfrequency) coefficients at the front of the vector and to place lowerenergy (and therefore higher frequency) transform coefficients at theback of the vector. In some examples, video encoder 200 may utilize apredefined scan order to scan the quantized transform coefficients toproduce a serialized vector, and then entropy encode the quantizedtransform coefficients of the vector. In other examples, video encoder200 may perform an adaptive scan. After scanning the quantized transformcoefficients to form the one-dimensional vector, video encoder 200 mayentropy encode the one-dimensional vector, e.g., according tocontext-adaptive binary arithmetic coding (CABAC). Video encoder 200 mayalso entropy encode values for syntax elements describing metadataassociated with the encoded video data for use by video decoder 300 indecoding the video data.

To perform CABAC, video encoder 200 may assign a context within acontext model to a symbol to be transmitted. The context may relate to,for example, whether neighboring values of the symbol are zero-valued ornot. The probability determination may be based on a context assigned tothe symbol.

Video encoder 200 may further generate syntax data, such as block-basedsyntax data, picture-based syntax data, and sequence-based syntax data,to video decoder 300, e.g., in a picture header, a block header, a sliceheader, or other syntax data, such as a sequence parameter set (SPS),picture parameter set (PPS), or video parameter set (VPS). Video decoder300 may likewise decode such syntax data to determine how to decodecorresponding video data.

In this manner, video encoder 200 may generate a bitstream includingencoded video data, e.g., syntax elements describing partitioning of apicture into blocks (e.g., CUs) and prediction and/or residualinformation for the blocks. Ultimately, video decoder 300 may receivethe bitstream and decode the encoded video data.

In general, video decoder 300 performs a reciprocal process to thatperformed by video encoder 200 to decode the encoded video data of thebitstream. For example, video decoder 300 may decode values for syntaxelements of the bitstream using CABAC in a manner substantially similarto, albeit reciprocal to, the CABAC encoding process of video encoder200. The syntax elements may define partitioning information of apicture into CTUs, and partitioning of each CTU according to acorresponding partition structure, such as a QTBT structure, to defineCUs of the CTU. The syntax elements may further define prediction andresidual information for blocks (e.g., CUs) of video data.

The residual information may be represented by, for example, quantizedtransform coefficients. Video decoder 300 may inverse quantize andinverse transform the quantized transform coefficients of a block toreproduce a residual block for the block. Video decoder 300 uses asignaled prediction mode (intra- or inter-prediction) and relatedprediction information (e.g., motion information for inter-prediction)to form a prediction block for the block. Video decoder 300 may thencombine the prediction block and the residual block (on asample-by-sample basis) to reproduce the original block. Video decoder300 may perform additional processing, such as performing a deblockingprocess to reduce visual artifacts along boundaries of the block.

This disclosure may generally refer to “signaling” certain information,such as syntax elements. The term “signaling” may generally refer to thecommunication of values for syntax elements and/or other data used todecode encoded video data. That is, video encoder 200 may signal valuesfor syntax elements in the bitstream. In general, signaling refers togenerating a value in the bitstream. As noted above, source device 102may transport the bitstream to destination device 116 substantially inreal time, or not in real time, such as might occur when storing syntaxelements to storage device 112 for later retrieval by destination device116.

According to aspects of PDPC, the prediction sample pred(x,y) located at(x, y) is predicted with an intra prediction mode (DC, planar, angular)and its value is modified using the PDPC expression for a singlereference sample line:pred(x,y)=(wL×R _(−1,y) +wT×R _(x,−1) −wTL×R_(−1,−1)+(64−wL−wT+wTL)×pred(x,y)=32)>>6,  (Eq. 1)where R_(x,−1), R_(−1,y) represent the reference samples located at thetop and left of current sample (x, y), respectively, and R_(−1,−1)represents the reference sample located at the top-left corner of thecurrent block. For the DC mode, the weights are calculated as followsfor a block with dimensions width and height:wT=32>>((y<<1)>>shift),wL=32>>((x<<1)>>shift),wTL=(wL>>4)+(wT>>4),with shift=(log₂(width)+log₂(height)+2)>>2,while for planar mode wTL=0, for horizontal mode wTL=wT and for verticalmode wTL=wL. The PDPC weights can be calculated with adds and shiftsonly. The value of pred(x,y) can be computed in a single step using Eq.1.

In some examples, video encoder 200 and video decoder 300 may beconfigured to perform a weighted combination of an intra-predictionblock (which may have had PDPC applied) and an inter-prediction block,where the weights may be sample-position-dependent. That is, videoencoder 200 and video decoder 300 may determine the weights for eachsample of the inter- and intra-prediction blocks based on a position ofthe corresponding sample. Thus, for each sample, video encoder 200 andvideo decoder 300 may determine corresponding weights, and then applythe weights to co-located samples of the inter- and intra-predictionblocks when combining the inter- and intra-prediction blocks to form aprediction block for a current block. Video encoder 200 may encode thecurrent block using the prediction block, while video decoder 300 maydecode the current block using the prediction block.

The weights for a given sample position may be set to have a common sum.For example, the sum of the weights applied to a sample co-located at acommon position within an inter- and an intra-prediction block may addup to a top range value for the weights, e.g., 32. Thus, the weight tobe applied to the inter-prediction block sample at position (x,y) maybe, e.g., wB(x,y), and the weight to be applied to the intra-predictionblock sample at position (x,y) may be, e.g., (32−wB(x,y)). Furthermore,different positions may have different, respective weight values. Thus,weight value wB(x₁,y₁) may be different than weight value wB(x₂,y₂).

FIG. 2 is a diagram illustrating examples of DC mode PDPC weights (wL,wT, wTL) for (0, 0) and (1, 0) positions inside one 4×4 block. If PDPCis applied to DC, planar, horizontal, and vertical intra modes,additional boundary filters are not applied, such as the DC modeboundary filter or horizontal/vertical mode edge filters. The Eq. 1equation may be generalized to include additional reference samplelines. In this case, multiple reference samples are available in theneighborhoods of R_(x,−1), R_(−1,y), R_(−1,−1) and each may have aweight assigned that can be optimized, for example, by training.

Provisional U.S. Patent Application No. 62/651,424 (filed on 2 Apr.2018, and the entire content of which is incorporated herein byreference) extends PDPC to the diagonal intra modes and to the angularmodes that are adjacent to the diagonal modes. The intended diagonalintra modes are the modes that predict according to the bottom-left andtop-right directions, as well as several adjacent angular modes, forexample, N adjacent modes between the bottom-left diagonal mode andvertical mode, and N or M adjacent modes between the top-right diagonalmode and horizontal mode.

FIG. 3 is a diagram illustrating the identification of the angularmodes. In general, the adjacent modes may be a selected subset ofavailable angular modes. The spacing between angular modes may benonuniform and some angular modes may be skipped.

FIGS. 4A-4D are conceptual diagrams illustrating PDPC definitions. FIG.4A illustrates the definition of reference samples R_(x,−1), R_(−1,y)and R_(−1,−1) for the extension of PDPC to the top-right diagonal mode.The prediction sample pred(x′, y′) is located at (x′, y′) within theprediction block. The coordinate x of the reference sample R_(x,−1) isgiven by: x=x′+y′+1, and the coordinate y of the reference sampleR_(−1,y) is similarly given by: y=x′+y′+1. The PDPC weights for thetop-right diagonal mode are, for example:wT=16>>((y′<<1)>>shift),wL=16>>((x′<<1)>>shift),wTL=0.

Similarly, FIG. 4B illustrates the definition of reference samplesR_(x,−1), R_(−1,y) and R_(−1,−1) for the extension of PDPC to thebottom-left diagonal mode. The coordinate x of the reference sampleR_(x,−1) is given by: x=x′+y′+1, and the coordinate y of the referencesample R_(−1,y) is: y=x′+y′+1. The PDPC weights for the top-rightdiagonal mode are, for example:wT=16>>((y′<<1)>>shift),wL=16>>((x′<<1)>>shift),wTL=0.

The case of an adjacent top-right diagonal mode is illustrated in FIG.4C. In general, for the angle α defined in FIG. 3 , the y coordinate ofthe reference sample R_(−1,y) is determined as follows:y=y′+tan(α)×(x′+1), and the x coordinate of R_(x,−1) is given by:x=x′+cotan(α)×(y′+1), with tan(α) and cotan(α) the tangent and cotangentof the angle α, respectively. The PDPC weights for an adjacent top-rightdiagonal mode are, for example:wT=32>>((y′<<1)>>shift),wL=32>>((x′<<1)>>shift),wTL=0, orwT=32>>((y′<<1)>>shift),wL=0,wTL=0.

Similarly, the case of an adjacent bottom-left diagonal mode isillustrated in FIG. 4D. In general, for the angle β defined in FIG. 3 ,the x coordinate of the reference sample R_(x,−1) is determined asfollows: x=x′+tan(β)×(y′+1), and the y coordinate of R_(−1,y) is givenby: y=y′+cotan(β)×(x′+1), with tan(β) and cotan(β) the tangent andcotangent of the angle β, respectively. The PDPC weights for an adjacentbottom-left diagonal mode are, for example:wL=32>>((x′<<1)>>shift),wT=32>>((y′<<1)>>shift),wTL=0, orwL=32>>((x′<<1)>>shift),wT=0,wTL=0.

As is the case for DC, planar, horizontal and vertical mode PDPC, thereis no additional boundary filtering, for example specified in “Algorithmdescription of Joint Exploration Test Model 7,” 7th JVET Meeting,Torino, Italy, July 2017, JVET-G1001 by J. Chen, E. Alshina, G. J.Sullivan, J.-R. Ohm, and J. Boyce.

FIG. 5 is a diagram illustrating example intra prediction modes. Anexample of intra prediction is wide-angle intra prediction. In someexamples, the intra prediction of a luma block includes 35 modes,including the Planar prediction mode, DC prediction mode and 33 angular(or directional) prediction modes. Directional prediction for squareblocks uses directions between −135 degrees to 45 degrees of the currentblock in the VVC test model 2 (VTM2) (see “Algorithm description forVersatile Video Coding and Test Model 2 (VTM2),” 11th JVET Meeting,Ljubljana, SI, July 2018, JVET-K1002 by J. Chen, Y. Ye, and S. Kim), asillustrated in FIG. 5 . The 35 modes of the intra prediction are indexedas shown in Table 1 below.

TABLE 1 Specification of intra prediction mode and associated namesIntra prediction mode Associated name 0 INTRA_PLANAR 1 INTRA_DC 2 . . .34 INTRA_ANGULAR2 . . . INTRA_ANGULAR34

In VTM2, the block structure used for specifying the prediction blockfor intra prediction is not restricted to be square (width w=height h).Rectangular prediction blocks (w>h or w<h) can increase the codingefficiency based on the characteristics of the content.

In such rectangular blocks, restricting the direction of intraprediction to be within −135 degrees to 45 degrees can result insituations where farther reference samples are used rather than closerreference samples for intra prediction. Such a design is likely to havean impact on the coding efficiency. It may be more beneficial to havethe range of restrictions relaxed so that closer reference samples(beyond the −135 to 45-degree angle) be used for prediction. An exampleof such a case is given in FIG. 6 .

FIG. 6 is a block diagram illustrating an example of an 8×4 rectangularblock. in In the example of FIG. 6 , “closer” reference samples(indicated by circle 3002) are not used, but “farther” reference samples(indicated by circle 3006) may be used, due to restriction of intraprediction direction to be in the range of −135 degrees to 45 degrees.That is, in the example of FIG. 6 , some reference samples within −135degrees but farther than those indicated by circle 3002 may be used,while some reference samples are not used although they are closer thanother samples, e.g., closer than the samples indicated by circle 3006.

FIGS. 7A-7C are block diagrams providing illustrations of mode mappingprocesses for modes outside of diagonal direction ranges. In FIG. 7A, asquare block does not require angular mode remapping. FIG. 7Billustrates angular mode remapping for a horizontal non-square block.FIG. 7C illustrates angular mode remapping for a vertical non-squareblock.

FIG. 8 is a block diagram illustrating wide angles that are adopted inVTM2. During the 12th JVET meeting, a modification of wide-angle intraprediction was adopted into VVC test model 3 (VTM3), details of whichare available from (i) “CE3-related: Unification of angular intraprediction for square and non-square blocks,” 12th JVET Meeting, MacauSAR, CN, October 2018, JVET-L0279 by L. Zhao, X. Zhao, S. Liu, and X.Li; (ii) “Algorithm description for Versatile Video Coding and TestModel 3 (VTM3),” 12th JVET Meeting, Macau SAR, CN, October 2018,JVET-L1002 by J. Chen, Y. Ye, and S. Kim; and (iii) “Versatile VideoCoding (Draft 3),” 12th JVET Meeting, Macau SAR, CN, October 2018,JVET-L1001 by B. Bross, J. Chen, and S. Liu.

This adoption includes two modifications to unify the angular intraprediction for square and non-square blocks. First, angular predictiondirections are modified to cover diagonal directions of all blockshapes. Second, all angular directions are kept within the range betweenthe bottom-left diagonal direction and the top-right diagonal directionfor all block aspect ratios (square and non-square) as illustrated inFIG. 7 and described above. In addition, the number of reference samplesin the top reference row and left reference column are restricted to2*width+1 and 2*height+1 for all block shapes. In the example of FIG. 8, wide angles (−1 to −10, and 67 to 76) are depicted in addition to the65 angular modes.

FIG. 9 is a conceptual diagram illustrating wider angles that areadopted in VTM3. Although VTM3 defines 95 modes, for any block size,only 67 modes are allowed. The exact modes that are allowed depend onthe ratio of block width to block height. This is done by restrictingthe mode range for certain blocks sizes. FIG. 9 provides an illustrationof wide angles (−1 to −14, and 67 to 80) in VTM3 beyond modes 2 and 66for a total of 93 angular modes.

Table 2 below specifies the mapping table between predModeIntra and theangle parameter intraPredAngle in VTM3, further details of which areavailable from “Versatile Video Coding (Draft 3),” 12th JVET Meeting,Macau SAR, CN, October 2018, JVET-L1001 by B. Bross, J. Chen, and S.Liu.

TABLE 2 predModeIntra −14 −13 −12 −11 −10 −9 −8 −7 −6 −5 intraPredAngle512 341 256 171 128 102 86 73 64 57 predModeIntra −4 −3 −2 −1 2 3 4 5 67 intraPredAngle 51 45 39 35 32 29 26 23 20 18 predModeIntra 8 9 10 1112 13 14 15 16 17 intraPredAngle 16 14 12 10 8 6 4 3 2 1 predModeIntra18 19 20 21 22 23 24 25 26 27 intraPredAngle 0 −1 −2 −3 −4 −6 −8 −10 −12−14 predModeIntra 28 29 30 31 32 33 34 35 36 37 intraPredAngle −16 −18−20 −23 −26 −29 −32 −29 −26 −23 predModeIntra 38 39 40 41 42 43 44 45 4647 intraPredAngle −20 −18 −16 −14 −12 −10 −8 −6 −4 −3 predModeIntra 4849 50 51 52 53 54 55 56 57 intraPredAngle −2 −1 0 1 2 3 4 6 8 10predModeIntra 58 59 60 61 62 63 64 65 66 67 intraPredAngle 12 14 16 1820 23 26 29 32 35 predModeIntra 68 69 70 71 72 73 74 75 76 77intraPredAngle 39 45 51 57 64 73 86 102 128 171 predModeIntra 78 79 80intraPredAngle 256 341 512

The inverse angle parameter invAngle may be derived based onintraPredAngle as follows:

$\begin{matrix}{{invAngle} = {{Round}\left( \frac{256*32}{intraPredAngle} \right)}} & \left( {1 - 1} \right)\end{matrix}$

Note that intraPredAngle values that are multiples of 32 (i.e. values of0, 32, 64, 128, 256, 512 in this example) may correspond with predictionfrom non-fractional reference array samples, as is the case in the VTM3specification. Table 3 below illustrates diagonal modes correspondingwith various block aspect ratios.

TABLE 3 Diagonal modes corresponding with various block aspect ratios.Block aspect ratio (W/H) Diagonal modes 1 (square) 2, 34, 66 2 8, 28, 724 12, 24, 76 8 14, 22, 78 16 16, 20, 80 ½ −6, 40, 60 ¼ −10, 44, 56 ⅛−12, 46, 54 1/16 −14, 48, 52

MDIS and reference sample interpolation are described in the followingportions of this disclosure. In HEVC, before intra prediction, theneighboring reference samples are potentially filtered using a 2-taplinear or 3-tap (1,2,1)/4 filter. This process is known as intrareference smoothing, or mode-dependent intra smoothing (MDIS). In MDIS,given the intra prediction mode index predModeIntra and block size nTbS,it is decided whether the reference smoothing process is performed andif so which smoothing filter is used. The following text is the relatedparagraph from the HEVC specification:

“8.4.4.2.3 Filtering Process of Neighbouring Samples

Inputs to this process are:

-   the neighbouring samples p[x][y], with x=−1, y=−1 . . . nTbS*2−1 and    x=0 . . . nTbS*2−1, y=−1,    -   a variable nTbS specifying the transform block size.

Outputs of this process are the filtered samples pF[x][y], with x=−1,y=−1 . . . nTbS*2−1 and x=0 . . . nTbS*2−1, y=−1.

The variable filterFlag is derived as follows:

-   If one or more of the following conditions are true, filterFlag is    set equal to 0:    -   predModeIntra is equal to INTRA_DC.    -   nTbS is equal 4.-   Otherwise, the following applies:    -   The variable minDistVerHor is set equal to        Min(Abs(predModeIntra−26), Abs(predModeIntra−10)).    -   The variable intraHorVerDistThres[nTbS] is specified in Table        8-3.    -   The variable filterFlag is derived as follows:        -   If minDistVerHor is greater than intraHorVerDistThres[nTbS],            filterFlag is set equal to 1.        -   Otherwise, filterFlag is set equal to 0.

TABLE 8-3 Specification of intraHorVerDistThres[ nTbS ] for varioustransform block sizes nTbS = 8 nTbS = 16 nTbS = 32 intraHorVerDist 7 1 0Thres[ nTbS ]

When filterFlag is equal to 1, the following applies:

-   The variable biIntFlag is derived as follows:    -   If all of the following conditions are true, biIntFlag is set        equal to 1:        -   strong_intra_smoothing_enabled_flag is equal to 1        -   nTbS is equal to 32        -   Abs(p[−1][−1]+p[nTbS*2−1][−1]−2*p[nTbS−1][−1])<(1<<(BitDepth_(Y)−5))    -   Abs(p[−1][−1]+p[−1][nTbS*2−1]−2*p[−1][nTbS−1])<(1<<(BitDepth_(Y)−5))    -   Otherwise, biIntFlag is set equal to 0.-   The filtering is performed as follows:    -   If biIntFlag is equal to 1, the filtered sample values pF[x][y]        with x=−1, y=−1 . . . 63 and x=0 . . . 63, y=−1 are derived as        follows:        pF[−1][−1]=p[−1][−1]  (8-30)        pF[−1][y]=((63−y)*p[−1][−1]+(y+1)*p[−1][63]+32)>>6 for y=0 . . .        62  (8-31)        pF[−1][63]=p[−1][63]  (8-32)        pF[x][−1]=((63−x)*p[−1][−1]+(x+1)*p[63][−1]+32)>>6 for x=0 . . .        62  (8-33)        pF[63][−1]=p[63][−1]  (8-34)-   Otherwise (biIntFlag is equal to 0), the filtered sample values    pF[x][y] with x=−1, y=−1 . . . nTbS*2−1 and x=0 . . . nTbS*2−1, y=−1    are derived as follows:    pF[−1][−1]=(p[−1][0]+2*p[−1][−1]+p[0][−1]+2)>>2   (8-35)    pF[−1][y]=(p[−1][y+1]+2*p[−1][y]+p[−1][y−1]+2)>>2 for y=0 . . .    nTbS*2−2  (8-36)    pF[−1][nTbS*2−1]=p[−1][nTbS*2−1]   (8-37)    pF[x][−1]=(p[x−1][−1]+2*p[x][−1]+p[x+1][−1]+2)>>2 for x=0 . . .    nTbS*2−2  (8-38)    pF[nTbS*2−1][−1]=p[nTbS*2−1][−1]   (8-39)”

During JVET activities, the Joint Exploration Test Model (JEM) version 7(further details of which are available from “Algorithm description ofJoint Exploration Test Model 7,” 7th JVET Meeting, Torino, Italy, July2017, JVET-G1001 by J. Chen, E. Alshina, G. J. Sullivan, J.-R. Ohm, andJ. Boyce) was defined and the following version of the MDIS table wasincluded for luma blocks:

TABLE 4 sizeIndex Threshold[sizeIndex] 0 20 1 20 2 14 3 2 4 0 5 20 6 0

The block size index is defined as follows in JEM7:sizeIndex=(log 2(BlockWidth)−2+log 2(BlockHeight)−2)/2+2−1

Whether to apply the [1 2 1]/4 smoothing filter to the intra referencesamples is determined as follows:IntraModeDiff=min(abs(IntraModeIdx−HOR_IDX),abs(IntraModeIdx−VER_IDX))With HOR_IDX=18 and VER_IDX=50, because JEM7 has 65 directional intramodes (IntraModeIdx 2-66) in addition to planar (IntraModeIdx=0) and DC(IntraModeIdx=1) modes. The following condition determines whether toapply the smoothing filter:

IF IntraModeDiff>Threshold[sizeIndex] THEN “apply smoothing filter”

In the Joint Video Experts Team (JVET) and its VVC Test Model version 3(VTM3) (“Versatile Video Coding (Draft 3),” 12th JVET Meeting, MacauSAR, CN, October 2018, JVET-L1001 by B. Bross, J. Chen, and S. Liu), thefollowing MDIS table is included:

TABLE 5 sizeIndex Threshold[sizeIndex] 0 20 1 20 2 20 3 14 4 2 5 0 6 0 70

The block size index is defined as follows in VTM3:sizeIndex=(log 2(BlockWidth)+log 2(BlockHeight))/2

Whether to apply the [1 2 1]/4 smoothing filter to the non-fractionalintra reference samples or switch the interpolation filters betweensmoothing (e.g., Gaussian interpolation) and non-smoothing (e.g., cubicinterpolation) for fractional reference sample positions is determinedas follows (see also Provisional U.S. Patent Application Nos. 62/731,723filed 14 Sep. 2018, 62/727,341 filed 5 Sep. 2018, and 62/693,266 filed 2Jul. 2018, the entire contents of each of which are incorporated hereinby reference, as well as “Versatile Video Coding (Draft 3),” 12th JVETMeeting, Macau SAR, CN, October 2018, JVET-L1001 by B. Bross, J. Chen,and S. Liu): IntraModeDiff=min(abs(IntraModeIdx−HOR_IDX),abs(IntraModeIdx−VER_IDX)) with HOR_IDX=18 and VER_IDX=50 and thecondition:IF IntraModeDiff>Threshold[sizeIndex] THEN “apply smoothing”

In VTM3, for wide-angle modes with index <2 or >66, the intra smoothingcondition is set equal to true. The reason is that twovertically-adjacent predicted samples may use two non-adjacent referencesamples in the case of wide-angle intra prediction.

Aspects of intra-inter prediction blending are discussed in “CE10.1.1:Multi-hypothesis prediction for improving AMVP mode, skip or merge mode,and intra mode,” 12th JVET Meeting, Macau SAR, CN, October 2018,JVET-L0100 by M.-S. Chiang, C.-W. Hsu, Y.-W. Huang, and S.-M. Lei. Thefollowing text, bookended by quotation marks, provides an overview ofintra-inter prediction blending:

“Multi-hypothesis prediction is proposed for improving AMVP mode, skipor merge mode, and intra mode. Multi-hypothesis prediction is proposedto improve the existing prediction modes in inter pictures, includinguni-prediction of advanced motion vector prediction (AMVP) mode, skipand merge mode, and intra mode. The general concept is to combine anexisting prediction mode with an extra merge indexed prediction. Themerge indexed prediction is performed as in merge mode, where a mergeindex is signaled to acquire motion information for the motioncompensated prediction. The final prediction is the weighted average ofthe merge indexed prediction and the prediction generated by theexisting prediction mode, where different weights are applied dependingon the combinations.

Three inter combined prediction modes are tested to combine mergeindexed prediction with uni-prediction of AMVP mode, merge mode, andintra mode, respectively. When combined with uni-prediction of AMVPmode, one motion is acquired using the original syntax elements in AMVPmode while the other is acquired using the merge index, where totallytwo hypotheses are used. When combined with merge mode, implicitselection of succeeding merge candidate without signaling any additionalmerge index is used to acquire the additional motion information, whereat most two more hypotheses are used. When combined with intra mode,explicit signaling of intra mode for merge mode in inter coding unit(CU) is applied to generate the combined predictions, where one morehypothesis from intra mode is used. Different weights to generate thefinal prediction depending on the combinations are also tested.

When the multi-hypothesis prediction is applied to improve intra mode,multi-hypothesis prediction combines one intra prediction and one mergeindexed prediction. In a merge CU, one flag is signaled for merge modeto select an intra mode from an intra candidate list when the flag istrue. For luma component, the intra candidate list is derived from 4intra prediction modes including DC, planar, horizontal, and verticalmodes, and the size of the intra candidate list can be 3 or 4 dependingon the block shape. When the CU width is larger than the double of CUheight, horizontal mode is exclusive of the intra mode list and when theCU height is larger than the double of CU width, vertical mode isremoved from the intra mode list. One intra prediction mode selected bythe intra mode index and one merge indexed prediction selected by themerge index are combined using weighted average. For chroma component,DM may be applied without extra signaling. The weights for combiningpredictions are described as follow. When DC or planar mode is selectedor the CB width or height is smaller than 4, equal weights are applied.For those CBs with CB width and height larger than or equal to 4, whenhorizontal/vertical mode is selected, one CB is firstvertically/horizontally split into four equal-area regions. Each weightset, denoted as (w_intra_(i), w_inter_(i)), where i is from 1 to 4 and(w_intra₁, w_inter₁)=(6, 2), (w_intra₂, w_inter₂)=(5, 3), (w_intra₃,w_inter₃)=(3, 5), and (w_intra₄, w_inter₄)=(2, 6), will be applied to acorresponding region. (w_intra₁, w_inter₁) is for the region closest tothe reference samples and (w_intra₄, w_inter₄) is for the regionfarthest away from the reference samples. Then, the combined predictioncan be calculated by summing up the two weighted predictions andright-shifting 3 bits. Moreover, the intra prediction mode for the intrahypothesis of predictors can be saved for reference of the followingneighboring CUs.”

Aspects of triangular motion compensated prediction are described in“CE10.3.1.b: Triangular prediction unit mode,” 12th JVET Meeting, MacauSAR, CN, October 2018, JVET-L0124 by R.-L. Liao and C. S. Lim. Thefollowing text, bookended by quotation marks, and making reference toFIG. 10 provides an overview of triangular motion compensatedprediction.

“In the triangular prediction unit mode, a CU can be split using twotriangular prediction units, in either diagonal or inverse diagonaldirection. Each triangular prediction unit in the CU has its ownuni-prediction motion vector and reference frame index which are derivedfrom a uni-prediction candidate list. Triangular partitioning is onlyapplied to motion compensated prediction, which means that the transformand quantization process is applied to the whole CU formed by combiningthe two triangles together. The triangular prediction unit mode is onlyapplied to a CU which block size is larger than or equal to 8×8, and itscoding prediction mode is either skip or merge mode. As shown in FIG. 10, it splits a CU into two triangular prediction units, in eitherdiagonal or inverse diagonal direction.”

“CE10.3.1.b: Triangular prediction unit mode,” 12th JVET Meeting, MacauSAR, CN, October 2018, JVET-L0124 by R.-L. Liao and C. S. Lim alsodescribes aspects of the adaptive weighting process. The following text,bookended by quotation marks, and making reference to FIG. 11 providesan overview of the adaptive weighting process:

“After predicting each triangular prediction unit, an adaptive weightingprocess is applied to the diagonal edge between the two triangularprediction units to derive the final prediction for the whole CU. Twoweighting factor groups are listed as follows:

-   1st weighting factor group: {7/8, 6/8, 4/8, 2/8, 1/8} and {7/8, 4/8,    1/8} are used for the luminance and the chrominance samples,    respectively;-   2nd weighting factor group: {7/8, 6/8, 5/8, 4/8, 3/8, 2/8, 1/8} and    {6/8, 4/8, 2/8} are used for the luminance and the chrominance    samples, respectively.    One weighting factor group is selected based on the comparison of    the motion vectors of two triangular prediction units. The 2nd    weighting factor group is used when the reference pictures of the    two triangular prediction units are different from each other or    their motion vector difference is larger than 16 pixels. Otherwise,    the 1st weighting factor group is used. An example is shown in FIG.    11 .”

The various technologies described above present one or more potentialproblems/issues. For instance, let the prediction sample intraPred(x,y)located at (x, y) be predicted with an intra prediction mode (DC,planar, angular) and its value be modified using the PDPC expression fora single reference sample line to obtain the intraPredPDPC(x,y)prediction sample as follows:intraPredPDPC(x,y)=(wL×R _(−1,y) +wT×R _(x,−1) −wTL×R_(−1,−1)+(64−wL−wT+wTL)×intraPred(x,y)+32)>>6

where R_(x,−1), R_(−1,y) represent the reference samples located at thetop and left of current sample (x, y), respectively, and R_(−1, −1)represents the reference sample located at the top-left corner of thecurrent block. Intra-inter prediction blends this prediction sampleintraPredPDPC(x,y) with a merge mode prediction interPred(x,y), forexample, by simple averaging as follows:intraInterPred(x,y)=(intraPredPDPC(x,y)+interPred(x,y)+1)>>1A potential problem is that PDPC is applied before the intra-interblending step, which may adversely affect coding efficiency andimplementation complexity.

Secondly, in the case of triangular motion compensated prediction, thetwo triangular prediction units are only applied to a motion-compensatedor inter-predicted CU. Blending of one intra and one inter triangularprediction unit is not supported. There exist ambiguities as to how PDPCtogether with blending is applied in this case.

Thirdly, the MDIS filtering may be applied to the reference samples forintra prediction before intra-inter blending, which may adversely affectcoding efficiency and implementation complexity.

This disclosure describes various techniques address one or more of thepotential problems listed above. In various examples, the techniquesdescribed below may mitigate one or more of the potential problems, andin other examples, the techniques may eliminate one or more of thepotential problems. The techniques of this disclosure may be implementedindividually, or in some examples, various combinations of thetechniques may be implemented, whether concurrently or in any serialsequence.

According to some examples in accordance with this disclosure, videoencoder 200 and/or video decoder 300 may predict intra block samples byusing an intra mode together with PDPC, intraPredPDPC(x,y), and theinter prediction block samples, interPred(x,y), can be blended togetherby one of the following example intra-inter prediction blendingprocesses:

-   -   a. Averaging:        intraInterPred(x,y)=(intraPredPDPC(x,y)+interPred(x,y)+1)>>1    -   b. Weighting with position independent weight parameter wB,        e.g., if wB value range is 0 . . . 32:        intraInterPred(x,y)=(wB×intraPredPDPC(x,y)+(32−wB)×interPred(x,y)+16)>>5    -   c. Weighting with position dependent weight parameter wB(x,y),        e.g., if wB(x,y) value range is 0 . . . 32:        intraInterPred(x,y)=(wB(x,y)×intraPredPDPC(x,y)+(32−wB(x,y))×interPred(x,y)+16)>>5    -   d. Video encoder 200 and/or video decoder 300 may make the        weights dependent on the intra mode, e.g., for planar, DC,        directional, or wide-angle directional modes, different position        independent or position dependent weights can be applied.    -   e. Video encoder 200 and/or video decoder 300 may make the        weights dependent on the inter mode or motion data.    -   f. Video encoder 200 and/or video decoder 300 may make the        weights dependent on the block dimensions (width, height), on        the block area, block shape (square, rectangular, triangular, .        . . ).    -   g. Video encoder 200 and/or video decoder 300 may fully or        partially disable intra-inter prediction blending by applying        weights so that only one of the intra or inter modes is chosen        per block or per block sample. For example, in this manner        prediction units within the current block can be defined with        various shapes, e.g., triangular units.    -   h. Video encoder 200 and/or video decoder 300 may enable or        disable intra-inter prediction blending based on flags or values        coded in the bitstream (parameter sets, picture header, tile        header, slice header, etc.) or based on conditions dependent on        block dimensions, block area, block shape, prediction modes.

According to some examples in accordance with this disclosure, videoencoder 200 and/or video decoder 300 may predict intra block samples byusing an intra mode, i.e., without using PDPC, intraPred(x,y). In theseexamples, video encoder 200 and/or video decoder 300 may blend the interprediction block samples, interPred(x,y), together by one of thefollowing example intra-inter prediction blending processes:

-   -   a. Averaging:        intraInterPred(x,y)=(intraPred(x,y)+interPred(x,y)+1)>>1    -   b. Weighting with position independent weight parameter wB,        e.g., if wB value range is 0 . . . 32:        intraInterPred(x,y)=(wB×intraPred(x,y)+(32−wB)×interPred(x,y)+16)>>5    -   c. Weighting with position dependent weight parameter wB(x,y),        e.g., if wB(x,y) value range is 0 . . . 32:        intraInterPred(x,y)=(wB(x,y)×intraPred(x,y)+(32−wB(x,y))×interPred(x,y)+16)>>5    -   d. Video encoder 200 and/or video decoder 300 may make the        weights dependent on the intra mode, e.g., for planar, DC,        directional, or wide-angle directional modes, different position        independent or position dependent weights can be applied.    -   e. Video encoder 200 and/or video decoder 300 may make the        weights dependent on the inter mode or motion data.    -   f. Video encoder 200 and/or video decoder 300 may make the        weights dependent on the block dimensions (width, height), on        the block dimensions (width, height), on the block area, block        shape (square, rectangular, triangular,    -   g. Video encoder 200 and/or video decoder 300 may fully or        partially disable intra-inter prediction blending by applying        weights so that only one of the intra or inter modes is chosen        per block or per block sample. For example, in this manner        prediction units within the current block can be defined with        various shapes, e.g., triangular units.    -   h. Video encoder 200 and/or video decoder 300 may enable or        disable intra-inter prediction blending based on flags or values        coded in the bitstream (parameter sets, picture header, tile        header, slice header, etc.) or based on conditions dependent on        block dimensions, block area, block shape, prediction modes.

According to some examples in accordance with this disclosure, videoencoder 200 and/or video decoder 300 may predict intra block samples byusing an intra mode, i.e., without using PDPC or with PDPC,intraPred(x,y). In these examples, video encoder 200 and/or videodecoder 300 may blend the inter prediction block samples,interPred(x,y), and neighboring reconstructed reference samples from oneor multiple lines on the left or top of the current block together byone of the following example intra-inter prediction blending processes:

-   -   a. Averaging intraPred(x,y) and interPred(x,y), and blending        this average together with neighbouring reconstructed reference        samples by applying weights:        intraInterPred(x,y)=(wL×R _(−1,y) +wT×R _(x,−1) ×wTL×R        _(−1,−1)+(64×wL−wT+wTL)×((intrapred(x,y)+interpred(x,y)+1)>>1)+32)>>6        -   where R_(x,−1), R_(−1,y) represent the reference samples            located at the top and left of current sample (x, y),            respectively, and R_(−1,−1) represents the reference sample            located at the top-left corner of the current block.        -   i. Weights wL, wT, wTL can be position independent.        -   ii. Weights wL, wT, wTL can be position dependent and can be            computed or stored in a table or template.        -   iii. Weights wL, wT, wTL can be position independent, and            depend on the intra mode, or on the inter mode (or motion            data), or on both modes, of the prediction blocks in the            blending process.        -   iv. Weights wL, wT, wTL can be position dependent and depend            on the intra mode, e.g., PDPC weights can be applied            corresponding with the intra mode, e.g., DC mode weights:            wT=32>>((y<<1)>>shift),wL=32>>((x<<1)>>shift),wTL=(wL>>4)+(wT>>4),            with shift=(log₂(width)+log₂(height)+2)>>2        -   v. Weights wL, wT, wTL can be position dependent and depend            on the inter mode or motion data, e.g., motion vector            direction.    -   b. Weighting intraPred(x,y) and interPred(x,y) with position        independent weight wB, and blending this weighted average        together with neighbouring reconstructed reference samples by        applying weights:        intraInterPred(x,y)=(wL×R _(−1,y) +wT×R _(x,−1) −wTL×R        _(−1,−1)+(64−wL−wT+wTL)×((wB×intrapred(x,y)+(32−wB)×interpred(x,y)+16)>>5)+32)>>6    -   c. Weighting intraPred(x,y) and interPred(x,y) with position        dependent weight wB(x,y), and blending this weighted average        together with neighbouring reconstructed reference samples by        applying weights:        intraInterPred(x,y)=(wL×R _(−1,y) +wT×R _(x,−1) −wTL×R        _(−1,−1)+(64−wL−wT+wTL)×((wB(x,y)×intrapred(x,y)+(32−wB(x,y))×interPred(x,y)+16)>>5)+32)>>6    -   d. Weights can be dependent on the intra mode, e.g., for planar,        DC, directional, or wide-angle directional modes, different        position independent or position dependent weights can be        applied.    -   e. Weights can be dependent on the inter mode or motion data.    -   f. Weights can be dependent on the block dimensions (width,        height), on the block area, block shape (square, rectangular,        triangular, . . . ).    -   g. Intra-inter prediction blending can be fully or partially        disabled by applying weights so that only one of the intra or        inter modes is chosen per block or per block sample. For        example, in this manner prediction units within the current        block can be defined with various shapes, e.g., triangular        units.    -   h. Intra-inter prediction blending can be disabled based on        flags or values coded in the bitstream (parameter sets, picture        header, tile header, slice header, etc.) or based on conditions        dependent on block dimensions, block area, block shape,        prediction modes.    -   i. Neighbouring reconstructed reference samples can be filtered        with a smoothing filter, bilateral filter, etc. MDIS conditions        that are dependent on the intra mode and block size can be        applied to determine whether to use unfiltered or filtered        reference samples, or conditions can apply based on the inter        mode, motion data, intra mode, block dimensions, block area,        block shape, etc. This information can be obtained from        neighbouring, current, or co-located blocks.

According to some examples of this disclosure, video encoder 200 and/orvideo decoder 300 may choose the intra mode from all intra modes or froma select set of intra modes (e.g., planar, DC, horizontal, vertical), oronly a single intra mode can be allowed (e.g., planar). The allowedintra modes can depend on the modes of neighboring blocks.

According to some examples of this disclosure, video encoder 200 and/orvideo decoder 300 may choose the inter mode from all inter modes or froma select set of inter modes (e.g., skip, merge), or only a single intermode can be allowed (e.g., merge). The allowed inter modes can depend onthe modes of neighboring or co-located blocks.

According to some examples of this disclosure, intra-inter blending mayuse more than two predictions, e.g., two inter predictions and one intraprediction. According to some of these examples, neighboringreconstructed reference samples from one or multiple lines on the leftor top of the current block can be used.

According to some examples of this disclosure, when triangularprediction blocks are used to code a block, a PDPC-like combination maybe applied to one or more triangular prediction blocks. A PDPC-likecombination may involve combining a temporary predicted sample value(obtained by a prediction method), with one or more neighboringreference samples. In some instances, the combination may use differentweights for each term in the combination. In some such instances, theweights may depend on the position of the current sample with respect tothe current triangular block or the current block. Variousimplementations of these examples are listed below:

-   -   a. In some examples, the reference samples may also refer to        samples that belong to a triangular prediction block of the        current block.    -   b. In one example, wL, wT, wTL, and wR weights are defined for        left, top, top-left and right reference samples, respectively. A        PDPC-like combination for a sample s(x,y) at position (x,y) may        be defined as follows:        pred(x,y)=(WL×R _(x1(x),y1(x)) +wT×R _(x2(x)y2(x)) +wR×R        _(x3(x),y3(x)) −wTL×R _(−1,−1)+(64−wL−wT−wR+wTL)×s(x,y)+32)>>6        where (xN(x),yN(x)) specify sample locations of left, top and        right reference samples, respectively, used of for the PDPC-like        combination for sample s(x,y).

FIGS. 12A and 12B are conceptual diagrams illustrating an example of acombination for two samples. In FIGS. 12A and 12B, an 8×8 block is splitinto two triangular partition blocks. Weights may be defined to besimilar to the weights defined for PDPC based on the distance from thesample s(x,y) and shift operations. The weights may also depend on themode that is used for prediction. FIG. 12A shows how the PDPC-likecombination is applied to sample S using reference samples T, L, R andTL. For different positions of the sample S, the reference sampleschange. S is the current sample, and L, R, T and TL are the left, right,top and top-left reference samples of S, respectively.

FIGS. 13A-13D are conceptual diagrams illustrating examples of howreference samples may change by position of a sample S. In one example,the weights are defined such that the weights are non-zero only for somesamples within a certain distance (e.g., two or three sample values) ofthe diagonal line creating the two triangular partitions. In anotherexample, the location of one or more reference samples may be a functionof the row index corresponding to the sample; in another embodiment thelocation of one or more reference samples may be a function of thecolumn index corresponding to the sample. For example, FIGS. 13A-13Dshow how the left reference samples vary for a certain neighborhood ofsamples, with arrows showing how the samples and the reference sampleshave moved with respect the samples in FIG. 13A. Arrows in FIGS. 13B-13Dindicate the shift in the samples with respect to FIG. 13A. In FIGS.13A-13D, S is the current sample, and L, R, T and TL are the left,right, top and top-left reference samples of S, respectively. In FIG.13B, T, S, and R are shifted to the right. In FIG. 13C, T is shifted tothe right and L, S, and R are shifted to the bottom and to the right. InFIG. 13D, T is shifted two to the right, L is shifted to the bottom andto the right, and S and R are shifted to the bottom and two to theright.

In some examples, PDPC-like combination may not apply to a partitionblock of the current block, e.g., a first triangular block in thecurrent block. In other examples, weights associated with one or more ofthe reference samples may be set equal to 0 for a partition block, e.g.,a first partition block. In FIG. 13B, when the left triangular partitionblock is reconstructed first, the weight associated with right referencesample may be set equal to 0.

-   -   c) In one example, PDPC-like combination may be applied to an        intra-coded block, an inter-coded block, or an intra-inter        prediction blended block. In other examples, a PDPC-like        combination may be applied to intra-coded or inter-coded blocks;        one or more such combined blocks may then be blended using        another combination, e.g., using PDPC.    -   d) In one example, the application of PDPC to one or more        triangular prediction blocks may be controlled by an indicator        that video encoder 200 signals to video decoder 300 in the        bitstream (e.g., a flag specifying that PDPC is applied to a        triangular prediction block) or inferred/derived by a coder        depending on the block size, mode used for prediction, or other        characteristics of the current or neighboring blocks.

FIG. 14 is a block diagram illustrating an example video encoder 200that may perform the techniques of this disclosure. FIG. 14 is providedfor purposes of explanation and should not be considered limiting of thetechniques as broadly exemplified and described in this disclosure. Forpurposes of explanation, this disclosure describes video encoder 200 inthe context of video coding standards such as the HEVC video codingstandard and the H.266 video coding standard in development. However,the techniques of this disclosure are not limited to these video codingstandards and are applicable generally to video encoding and decoding.

In the example of FIG. 14 , video encoder 200 includes video data memory230, mode selection unit 202, residual generation unit 204, transformprocessing unit 206, quantization unit 208, inverse quantization unit210, inverse transform processing unit 212, reconstruction unit 214,filter unit 216, decoded picture buffer (DPB) 218, and entropy encodingunit 220. Any or all of video data memory 230, mode selection unit 202,residual generation unit 204, transform processing unit 206,quantization unit 208, inverse quantization unit 210, inverse transformprocessing unit 212, reconstruction unit 214, filter unit 216, DPB 218,and entropy encoding unit 220 may be implemented in one or moreprocessors or in processing circuitry. Moreover, video encoder 200 mayinclude additional or alternative processors or processing circuitry toperform these and other functions. Non-limiting examples of processingcircuitry that video encoder 200 may include are fixed functioncircuitry, programmable circuitry, and ASICs.

Video data memory 230 may store video data to be encoded by thecomponents of video encoder 200. Video encoder 200 may receive the videodata stored in video data memory 230 from, for example, video source 104(FIG. 1 ). DPB 218 may act as a reference picture memory that storesreference video data for use in prediction of subsequent video data byvideo encoder 200. Video data memory 230 and DPB 218 may be formed byany of a variety of memory devices, such as dynamic random access memory(DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM),resistive RAM (RRAM), or other types of memory devices. Video datamemory 230 and DPB 218 may be provided by the same memory device orseparate memory devices. In various examples, video data memory 230 maybe on-chip with other components of video encoder 200, as illustrated,or off-chip relative to those components.

In this disclosure, reference to video data memory 230 should not beinterpreted as being limited to memory internal to video encoder 200,unless specifically described as such, or memory external to videoencoder 200, unless specifically described as such. Rather, reference tovideo data memory 230 should be understood as reference memory thatstores video data that video encoder 200 receives for encoding (e.g.,video data for a current block that is to be encoded). Memory 106 ofFIG. 1 may also provide temporary storage of outputs from the variousunits of video encoder 200.

The various units of FIG. 14 are illustrated to assist withunderstanding the operations performed by video encoder 200. The unitsmay be implemented as fixed-function circuits, programmable circuits, ora combination thereof. Fixed-function circuits refer to circuits thatprovide particular functionality and are preset on the operations thatcan be performed. Programmable circuits refer to circuits that can beprogrammed to perform various tasks and provide flexible functionalityin the operations that can be performed. For instance, programmablecircuits may execute software or firmware that cause the programmablecircuits to operate in the manner defined by instructions of thesoftware or firmware. Fixed-function circuits may execute softwareinstructions (e.g., to receive parameters or output parameters), but thetypes of operations that the fixed-function circuits perform aregenerally immutable. In some examples, the one or more of the units maybe distinct circuit blocks (fixed-function or programmable), and in someexamples, the one or more units may be integrated circuits.

Video encoder 200 may include arithmetic logic units (ALUs), elementaryfunction units (EFUs), digital circuits, analog circuits, and/orprogrammable cores, formed from programmable circuits. In examples wherethe operations of video encoder 200 are performed using softwareexecuted by the programmable circuits, memory 106 (FIG. 1 ) may storethe object code of the software that video encoder 200 receives andexecutes, or another memory within video encoder 200 (not shown) maystore such instructions.

Video data memory 230 is configured to store received video data. Videoencoder 200 may retrieve a picture of the video data from video datamemory 230 and provide the video data to residual generation unit 204and mode selection unit 202. Video data in video data memory 230 may beraw video data that is to be encoded.

Mode selection unit 202 includes a motion estimation unit 222, motioncompensation unit 224, and an intra-prediction unit 226. Mode selectionunit 202 may include additional functional units to perform videoprediction in accordance with other prediction modes. As examples, modeselection unit 202 may include a palette unit, an intra-block copy unit(which may be part of motion estimation unit 222 and/or motioncompensation unit 224), an affine unit, a linear model (LM) unit, or thelike.

Mode selection unit 202 generally coordinates multiple encoding passesto test combinations of encoding parameters and resultingrate-distortion values for such combinations. The encoding parametersmay include partitioning of CTUs into CUs, prediction modes for the CUs,transform types for residual data of the CUs, quantization parametersfor residual data of the CUs, and so on. Mode selection unit 202 mayultimately select the combination of encoding parameters havingrate-distortion values that are better than the other testedcombinations.

Video encoder 200 may partition a picture retrieved from video datamemory 230 into a series of CTUs and encapsulate one or more CTUs withina slice. Mode selection unit 202 may partition a CTU of the picture inaccordance with a tree structure, such as the QTBT structure or thequad-tree structure of HEVC described above. As described above, videoencoder 200 may form one or more CUs from partitioning a CTU accordingto the tree structure. Such a CU may also be referred to generally as a“video block” or “block.”

In general, mode selection unit 202 also controls the components thereof(e.g., motion estimation unit 222, motion compensation unit 224, andintra-prediction unit 226) to generate a prediction block for a currentblock (e.g., a current CU, or in HEVC, the overlapping portion of a PUand a TU). For inter-prediction of a current block, motion estimationunit 222 may perform a motion search to identify one or more closelymatching reference blocks in one or more reference pictures (e.g., oneor more previously coded pictures stored in DPB 218). In particular,motion estimation unit 222 may calculate a value representative of howsimilar a potential reference block is to the current block, e.g.,according to sum of absolute difference (SAD), sum of squareddifferences (SSD), mean absolute difference (MAD), mean squareddifferences (MSD), or the like. Motion estimation unit 222 may generallyperform these calculations using sample-by-sample differences betweenthe current block and the reference block being considered. Motionestimation unit 222 may identify a reference block having a lowest valueresulting from these calculations, indicating a reference block thatmost closely matches the current block.

Motion estimation unit 222 may form one or more motion vectors (MVs)that defines the positions of the reference blocks in the referencepictures relative to the position of the current block in a currentpicture. Motion estimation unit 222 may then provide the motion vectorsto motion compensation unit 224. For example, for uni-directionalinter-prediction, motion estimation unit 222 may provide a single motionvector, whereas for bi-directional inter-prediction, motion estimationunit 222 may provide two motion vectors. Motion compensation unit 224may then generate a prediction block using the motion vectors. Forexample, motion compensation unit 224 may retrieve data of the referenceblock using the motion vector. As another example, if the motion vectorhas fractional sample precision, motion compensation unit 224 mayinterpolate values for the prediction block according to one or moreinterpolation filters. Moreover, for bi-directional inter-prediction,motion compensation unit 224 may retrieve data for two reference blocksidentified by respective motion vectors and combine the retrieved data,e.g., through sample-by-sample averaging or weighted averaging.

As another example, for intra-prediction, or intra-prediction coding,intra-prediction unit 226 may generate the prediction block from samplesneighboring the current block. For example, for directional modes,intra-prediction unit 226 may generally mathematically combine values ofneighboring samples and populate these calculated values in the defineddirection across the current block to produce the prediction block. Asanother example, for DC mode, intra-prediction unit 226 may calculate anaverage of the neighboring samples to the current block and generate theprediction block to include this resulting average for each sample ofthe prediction block. In some examples, a DC value for DC mode may bezero, in which case intra-prediction unit 226 may generate anintra-prediction block having all zero-valued samples.

According to the techniques of this disclosure, mode selection unit 202may also cause motion estimation unit 222 and motion compensation unit224 to generate an inter-prediction block for a current block of videodata, and intra-prediction unit 226 to generate an intra-predictionblock for the current block. Mode selection unit 202 may combine theinter-prediction block and the intra-prediction block to generate theprediction block for the current block according to the techniques ofthis disclosure. For example, mode selection unit 202 may performposition-dependent weighting of samples of the inter-prediction andintra-prediction blocks when generating the prediction block. That is,for each sample of a prediction block to be generated, mode selectionunit 202 may determine position-dependent weights corresponding to theposition of the sample in the prediction block.

Mode selection unit 202 may then apply the weights to the correspondingsamples of the intra-prediction block and the inter-prediction block togenerate a sample for the prediction block at the correspondingpositions. Because the weights may be position-dependent, differentpositions may have different weights for inter- and intra-predictionsamples. In some examples, all sets of inter- and intra-predictionweights may add up to the same value, e.g., an upper bound range value,such as 32. That is, for each position (x,y) in the prediction block,the sum of the intra-prediction weight and the inter-prediction weightmay be 32. Thus, the inter-prediction weight may be, for example,wB(x,y), and the intra-prediction weight may be (32−wB(x,y)).

In one example, to calculate values for samples of the prediction block,mode selection unit 202 may execute the following function for eachsample: (wB(x,y)×intraPredPDPC(x,y)+(32−wB(x,y)×interPred(x,y)+16)>>5,where (x,y) represents the position of the sample in the predictionblock, intraPredPDPC(x,y) represents the sample at position (x,y) in theintra-prediction block, interPred(x,y) represents the sample at position(x,y) in the inter-prediction block, wB(x,y) represents the firstweight, (32−wB(x,y)) represents the second weight, and ‘>>’ represents abitwise right shift operator.

As an alternative example, to calculate values for samples of theprediction block, mode selection unit 202 may execute the followingfunction for each sample:(wL×R_(x-1,y)+wT×R_(x,y-1)−wTL×R_(−1,−1)+(64−wL−wT+wTL)×((intrapred(x,y)+interpred(x,y)+1)>>1)+32)>>6,where R_(x-1,y) represents a left-neighboring reconstructed referencesample to the sample at the position in the current block, R_(x,y-1)represents an above-neighboring reconstructed reference sample to thesample at the position in the current block, wL represents aleft-neighboring weight, wT represents an above-neighboring weight, wTLrepresents a top-left weight, R_(−1,−1) represents a reference sample ata top-left corner of the current block, and ‘>>’ represents a bitwiseright shift operator.

Mode selection unit 202 provides the prediction block to residualgeneration unit 204. Residual generation unit 204 receives a raw,uncoded version of the current block from video data memory 230 and theprediction block from mode selection unit 202. Residual generation unit204 calculates sample-by-sample differences between the current blockand the prediction block. The resulting sample-by-sample differencesdefine a residual block for the current block. In some examples,residual generation unit 204 may also determine differences betweensample values in the residual block to generate a residual block usingresidual differential pulse code modulation (RDPCM). In some examples,residual generation unit 204 may be formed using one or more subtractorcircuits that perform binary subtraction.

In examples where mode selection unit 202 partitions CUs into PUs, eachPU may be associated with a luma prediction unit and correspondingchroma prediction units. Video encoder 200 and video decoder 300 maysupport PUs having various sizes. As indicated above, the size of a CUmay refer to the size of the luma coding block of the CU and the size ofa PU may refer to the size of a luma prediction unit of the PU. Assumingthat the size of a particular CU is 2N×2N, video encoder 200 may supportPU sizes of 2N×2N or N×N for intra prediction, and symmetric PU sizes of2N×2N, 2N×N, N×2N, N×N, or similar for inter prediction. Video encoder200 and video decoder 300 may also support asymmetric partitioning forPU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter prediction.

In examples where mode selection unit 202 does not further partition aCU into PUs, each CU may be associated with a luma coding block andcorresponding chroma coding blocks. As above, the size of a CU may referto the size of the luma coding block of the CU. The video encoder 200and video decoder 300 may support CU sizes of 2N×2N, 2N×N, or N×2N.

For other video coding techniques such as an intra-block copy modecoding, an affine-mode coding, and linear model (LM) mode coding, as fewexamples, mode selection unit 202, via respective units associated withthe coding techniques, generates a prediction block for the currentblock being encoded. In some examples, such as palette mode coding, modeselection unit 202 may not generate a prediction block, and insteadgenerate syntax elements that indicate the manner in which toreconstruct the block based on a selected palette. In such modes, modeselection unit 202 may provide these syntax elements to entropy encodingunit 220 to be encoded.

As described above, residual generation unit 204 receives the video datafor the current block and the corresponding prediction block. Residualgeneration unit 204 then generates a residual block for the currentblock. To generate the residual block, residual generation unit 204calculates sample-by-sample differences between the prediction block andthe current block.

Transform processing unit 206 applies one or more transforms to theresidual block to generate a block of transform coefficients (referredto herein as a “transform coefficient block”). Transform processing unit206 may apply various transforms to a residual block to form thetransform coefficient block. For example, transform processing unit 206may apply a discrete cosine transform (DCT), a directional transform, aKarhunen-Loeve transform (KLT), or a conceptually similar transform to aresidual block. In some examples, transform processing unit 206 mayperform multiple transforms to a residual block, e.g., a primarytransform and a secondary transform, such as a rotational transform. Insome examples, transform processing unit 206 does not apply transformsto a residual block.

Quantization unit 208 may quantize the transform coefficients in atransform coefficient block, to produce a quantized transformcoefficient block. Quantization unit 208 may quantize transformcoefficients of a transform coefficient block according to aquantization parameter (QP) value associated with the current block.Video encoder 200 (e.g., via mode selection unit 202) may adjust thedegree of quantization applied to the coefficient blocks associated withthe current block by adjusting the QP value associated with the CU.Quantization may introduce loss of information, and thus, quantizedtransform coefficients may have lower precision than the originaltransform coefficients produced by transform processing unit 206.

Inverse quantization unit 210 and inverse transform processing unit 212may apply inverse quantization and inverse transforms to a quantizedtransform coefficient block, respectively, to reconstruct a residualblock from the transform coefficient block. Reconstruction unit 214 mayproduce a reconstructed block corresponding to the current block (albeitpotentially with some degree of distortion) based on the reconstructedresidual block and a prediction block generated by mode selection unit202. For example, reconstruction unit 214 may add samples of thereconstructed residual block to corresponding samples from theprediction block generated by mode selection unit 202 to produce thereconstructed block.

Filter unit 216 may perform one or more filter operations onreconstructed blocks. For example, filter unit 216 may performdeblocking operations to reduce blockiness artifacts along edges of CUs.Operations of filter unit 216 may be skipped, in some examples.

Video encoder 200 stores reconstructed blocks in DPB 218. For instance,in examples where operations of filter unit 216 are not needed,reconstruction unit 214 may store reconstructed blocks to DPB 218. Inexamples where operations of filter unit 216 are needed, filter unit 216may store the filtered reconstructed blocks to DPB 218. Motionestimation unit 222 and motion compensation unit 224 may retrieve areference picture from DPB 218, formed from the reconstructed (andpotentially filtered) blocks, to inter-predict blocks of subsequentlyencoded pictures. In addition, intra-prediction unit 226 may usereconstructed blocks in DPB 218 of a current picture to intra-predictother blocks in the current picture.

In general, entropy encoding unit 220 may entropy encode syntax elementsreceived from other functional components of video encoder 200. Forexample, entropy encoding unit 220 may entropy encode quantizedtransform coefficient blocks from quantization unit 208. As anotherexample, entropy encoding unit 220 may entropy encode prediction syntaxelements (e.g., motion information for inter-prediction or intra-modeinformation for intra-prediction) from mode selection unit 202. Entropyencoding unit 220 may perform one or more entropy encoding operations onthe syntax elements, which are another example of video data, togenerate entropy-encoded data. For example, entropy encoding unit 220may perform a context-adaptive variable length coding (CAVLC) operation,a CABAC operation, a variable-to-variable (V2V) length coding operation,a syntax-based context-adaptive binary arithmetic coding (SBAC)operation, a Probability Interval Partitioning Entropy (PIPE) codingoperation, an Exponential-Golomb encoding operation, or another type ofentropy encoding operation on the data. In some examples, entropyencoding unit 220 may operate in bypass mode where syntax elements arenot entropy encoded.

Video encoder 200 may output a bitstream that includes the entropyencoded syntax elements needed to reconstruct blocks of a slice orpicture. In particular, entropy encoding unit 220 may output thebitstream.

The operations described above are described with respect to a block.Such description should be understood as being operations for a lumacoding block and/or chroma coding blocks. As described above, in someexamples, the luma coding block and chroma coding blocks are luma andchroma components of a CU. In some examples, the luma coding block andthe chroma coding blocks are luma and chroma components of a PU.

In some examples, operations performed with respect to a luma codingblock need not be repeated for the chroma coding blocks. As one example,operations to identify a motion vector (MV) and reference picture for aluma coding block need not be repeated for identifying a MV andreference picture for the chroma blocks. Rather, the MV for the lumacoding block may be scaled to determine the MV for the chroma blocks,and the reference picture may be the same. As another example, theintra-prediction process may be the same for the luma coding blocks andthe chroma coding blocks.

In this manner, video encoder 200 represents an example of a video codercomprising a memory configured to store video data and one or moreprocessors implemented in circuitry and configured to generate aninter-prediction block for a current block of the video data; generatean intra-prediction block for the current block; generate a predictionblock for the current block, wherein to generate the prediction block,the one or more processors are configured to, for each sample of theprediction block: determine a first weight for the sample according to aposition of the sample in the prediction block; determine a secondweight for the sample according to the position of the sample in theprediction block; apply the first weight to a sample at the position inthe inter-prediction block to generate a weighted inter-predictionsample; apply the second weight to a sample at the position in theintra-prediction block to generate a weighted intra-prediction sample;and calculate a value for the sample at the position in the predictionblock using the weighted inter-prediction sample and the weightedintra-prediction sample; and code the current block using the predictionblock.

FIG. 15 is a block diagram illustrating an example video decoder 300that may perform the techniques of this disclosure. FIG. 15 is providedfor purposes of explanation and is not limiting on the techniques asbroadly exemplified and described in this disclosure. For purposes ofexplanation, this disclosure describes video decoder 300 is describedaccording to the techniques of JEM and HEVC. However, the techniques ofthis disclosure may be performed by video coding devices that areconfigured to other video coding standards.

In the example of FIG. 15 , video decoder 300 includes coded picturebuffer (CPB) memory 320, entropy decoding unit 302, predictionprocessing unit 304, inverse quantization unit 306, inverse transformprocessing unit 308, reconstruction unit 310, filter unit 312, anddecoded picture buffer (DPB) 314. Any or all of CPB memory 320, entropydecoding unit 302, prediction processing unit 304, inverse quantizationunit 306, inverse transform processing unit 308, reconstruction unit310, filter unit 312, and DPB 314 may be implemented in one or moreprocessors or in processing circuitry. Moreover, video decoder 300 mayinclude additional or alternative processors or processing circuitry toperform these and other functions. Non-limiting examples of processingcircuitry that video decoder 300 may include are fixed functioncircuitry, programmable circuitry, and ASICs.

Prediction processing unit 304 includes motion compensation unit 316 andintra-prediction unit 318. Prediction processing unit 304 may includeaddition units to perform prediction in accordance with other predictionmodes. As examples, prediction processing unit 304 may include a paletteunit, an intra-block copy unit (which may form part of motioncompensation unit 316), an affine unit, a linear model (LM) unit, or thelike. In other examples, video decoder 300 may include more, fewer, ordifferent functional components.

CPB memory 320 may store video data, such as an encoded video bitstream,to be decoded by the components of video decoder 300. The video datastored in CPB memory 320 may be obtained, for example, fromcomputer-readable medium 110 (FIG. 1 ). CPB memory 320 may include a CPBthat stores encoded video data (e.g., syntax elements) from an encodedvideo bitstream. Also, CPB memory 320 may store video data other thansyntax elements of a coded picture, such as temporary data representingoutputs from the various units of video decoder 300. DPB 314 generallystores decoded pictures, which video decoder 300 may output and/or useas reference video data when decoding subsequent data or pictures of theencoded video bitstream. CPB memory 320 and DPB 314 may be formed by anyof a variety of memory devices, such as dynamic random access memory(DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM),resistive RAM (RRAM), or other types of memory devices. CPB memory 320and DPB 314 may be provided by the same memory device or separate memorydevices. In various examples, CPB memory 320 may be on-chip with othercomponents of video decoder 300, or off-chip relative to thosecomponents.

Additionally or alternatively, in some examples, video decoder 300 mayretrieve coded video data from memory 120 (FIG. 1 ). That is, memory 120may store data as discussed above with CPB memory 320. Likewise, memory120 may store instructions to be executed by video decoder 300, whensome or all of the functionality of video decoder 300 is implemented insoftware to executed by processing circuitry of video decoder 300.

The various units shown in FIG. 15 are illustrated to assist withunderstanding the operations performed by video decoder 300. The unitsmay be implemented as fixed-function circuits, programmable circuits, ora combination thereof. Similar to FIG. 14 , fixed-function circuitsrefer to circuits that provide particular functionality, and are preseton the operations that can be performed. Programmable circuits refer tocircuits that can be programmed to perform various tasks, and provideflexible functionality in the operations that can be performed. Forinstance, programmable circuits may execute software or firmware thatcause the programmable circuits to operate in the manner defined byinstructions of the software or firmware. Fixed-function circuits mayexecute software instructions (e.g., to receive parameters or outputparameters), but the types of operations that the fixed-functioncircuits perform are generally immutable. In some examples, the one ormore of the units may be distinct circuit blocks (fixed-function orprogrammable), and in some examples, the one or more units may beintegrated circuits.

Video decoder 300 may include ALUs, EFUs, digital circuits, analogcircuits, and/or programmable cores formed from programmable circuits.In examples where the operations of video decoder 300 are performed bysoftware executing on the programmable circuits, on-chip or off-chipmemory may store instructions (e.g., object code) of the software thatvideo decoder 300 receives and executes.

Entropy decoding unit 302 may receive encoded video data from the CPBand entropy decode the video data to reproduce syntax elements.Prediction processing unit 304, inverse quantization unit 306, inversetransform processing unit 308, reconstruction unit 310, and filter unit312 may generate decoded video data based on the syntax elementsextracted from the bitstream.

In general, video decoder 300 reconstructs a picture on a block-by-blockbasis. Video decoder 300 may perform a reconstruction operation on eachblock individually (where the block currently being reconstructed, i.e.,decoded, may be referred to as a “current block”).

Entropy decoding unit 302 may entropy decode syntax elements definingquantized transform coefficients of a quantized transform coefficientblock, as well as transform information, such as a quantizationparameter (QP) and/or transform mode indication(s). Inverse quantizationunit 306 may use the QP associated with the quantized transformcoefficient block to determine a degree of quantization and, likewise, adegree of inverse quantization for inverse quantization unit 306 toapply. Inverse quantization unit 306 may, for example, perform a bitwiseleft-shift operation to inverse quantize the quantized transformcoefficients. Inverse quantization unit 306 may thereby form a transformcoefficient block including transform coefficients.

After inverse quantization unit 306 forms the transform coefficientblock, inverse transform processing unit 308 may apply one or moreinverse transforms to the transform coefficient block to generate aresidual block associated with the current block. For example, inversetransform processing unit 308 may apply an inverse DCT, an inverseinteger transform, an inverse Karhunen-Loeve transform (KLT), an inverserotational transform, an inverse directional transform, or anotherinverse transform to the coefficient block.

Furthermore, prediction processing unit 304 generates a prediction blockaccording to prediction information syntax elements that were entropydecoded by entropy decoding unit 302. For example, if the predictioninformation syntax elements indicate that the current block isinter-predicted, motion compensation unit 316 may generate theprediction block. In this case, the prediction information syntaxelements may indicate a reference picture in DPB 314 from which toretrieve a reference block, as well as a motion vector identifying alocation of the reference block in the reference picture relative to thelocation of the current block in the current picture. Motioncompensation unit 316 may generally perform the inter-prediction processin a manner that is substantially similar to that described with respectto motion compensation unit 224 (FIG. 14 ).

As another example, if the prediction information syntax elementsindicate that the current block is intra-predicted, intra-predictionunit 318 may generate the prediction block according to anintra-prediction mode indicated by the prediction information syntaxelements. Again, intra-prediction unit 318 may generally perform theintra-prediction process in a manner that is substantially similar tothat described with respect to intra-prediction unit 226 (FIG. 14 ).Intra-prediction unit 318 may retrieve data of neighboring samples tothe current block from DPB 314.

According to the techniques of this disclosure, prediction processingunit 304 may also motion compensation unit 316 to generate aninter-prediction block for a current block of video data, andintra-prediction unit 318 to generate an intra-prediction block for thecurrent block. Prediction processing unit 304 may combine theinter-prediction block and the intra-prediction block to generate theprediction block for the current block according to the techniques ofthis disclosure. For example, prediction processing unit 304 may performposition-dependent weighting of samples of the inter-prediction andintra-prediction blocks when generating the prediction block. That is,for each sample of a prediction block to be generated, predictionprocessing unit 304 may determine position-dependent weightscorresponding to the position of the sample in the prediction block.

Prediction processing unit 304 may then apply the weights to thecorresponding samples of the intra-prediction block and theinter-prediction block to generate a sample for the prediction block atthe corresponding positions. Because the weights may beposition-dependent, different positions may have different weights forinter- and intra-prediction samples. In some examples, all sets ofinter- and intra-prediction weights may add up to the same value, e.g.,an upper bound range value, such as 32. That is, for each position (x,y)in the prediction block, the sum of the intra-prediction weight and theinter-prediction weight may be 32. Thus, the inter-prediction weight maybe, for example, wB(x,y), and the intra-prediction weight may be(32−wB(x,y)).

In one example, to calculate values for samples of the prediction block,prediction processing unit 304 may execute the following function foreach sample:(wB(x,y)×intraPredPDPC(x,y)+(32−wB(x,y)×interPred(x,y)+16)>>5, where(x,y) represents the position of the sample in the prediction block,intraPredPDPC(x,y) represents the sample at position (x,y) in theintra-prediction block, interPred(x,y) represents the sample at position(x,y) in the inter-prediction block, wB(x,y) represents the firstweight, (32−wB(x,y)) represents the second weight, and ‘>>’ represents abitwise right shift operator.

As an alternative example, to calculate values for samples of theprediction block, prediction processing unit 304 may execute thefollowing function for each sample:(wL×R_(x-1,y)+wT×R_(x,y-1)−wTL×R_(−1,−1)+(64−wL−wT+wTL)×((intrapred(x,y)+interpred(x,y)+1)>>1)+32)>>6,where R_(x-1,y) represents a left-neighboring reconstructed referencesample to the sample at the position in the current block, R_(x,y-1)represents an above-neighboring reconstructed reference sample to thesample at the position in the current block, wL represents aleft-neighboring weight, wT represents an above-neighboring weight, wTLrepresents a top-left weight, R_(−1,−1) represents a reference sample ata top-left corner of the current block, and ‘>>’ represents a bitwiseright shift operator.

Reconstruction unit 310 may reconstruct the current block using theprediction block and the residual block. For example, reconstructionunit 310 may add samples of the residual block to corresponding samplesof the prediction block to reconstruct the current block.

Filter unit 312 may perform one or more filter operations onreconstructed blocks. For example, filter unit 312 may performdeblocking operations to reduce blockiness artifacts along edges of thereconstructed blocks. Operations of filter unit 312 are not necessarilyperformed in all examples.

Video decoder 300 may store the reconstructed blocks in DPB 314. Asdiscussed above, DPB 314 may provide reference information, such assamples of a current picture for intra-prediction and previously decodedpictures for subsequent motion compensation, to prediction processingunit 304. Moreover, video decoder 300 may output decoded pictures fromDPB for subsequent presentation on a display device, such as displaydevice 118 of FIG. 1 .

In this manner, video decoder 300 represents an example of a device fordecoding video data including a memory configured to store video data,and one or more processing units implemented in processing circuitry andconfigured to generate an inter-prediction block for a current block ofthe video data; generate an intra-prediction block for the currentblock; generate a prediction block for the current block, wherein togenerate the prediction block, the one or more processors are configuredto, for each sample of the prediction block: determine a first weightfor the sample according to a position of the sample in the predictionblock; determine a second weight for the sample according to theposition of the sample in the prediction block; apply the first weightto a sample at the position in the inter-prediction block to generate aweighted inter-prediction sample; apply the second weight to a sample atthe position in the intra-prediction block to generate a weightedintra-prediction sample; and calculate a value for the sample at theposition in the prediction block using the weighted inter-predictionsample and the weighted intra-prediction sample; and code the currentblock using the prediction block.

FIG. 16 is a flowchart illustrating an example method of encoding videodata according to the techniques of this disclosure. Although describedwith respect to video encoder 200 (FIGS. 1 and 14 ), it should beunderstood that other devices may be configured to perform a methodsimilar to that of FIG. 16 .

In this example, video encoder 200 initially predicts the current blockaccording to the techniques of this disclosure. In particular, videoencoder 200 generates an intra-prediction block for the current block(350) and generates an inter-prediction block for the current block(352). Video encoder 200 may then determine sample position-dependentweights (354). That is, for each sample of the intra- andinter-prediction blocks, video encoder 200 may determine respectiveweights. In some examples, the sum of the intra-prediction weight andthe inter-prediction weight may be a common value, such as a maximumrange value, e.g., 32. Thus, for example, the intra-prediction weightmay be referred to as wB and the inter-prediction weight may be (32−wB).

Video encoder 200 may apply the weights to the respective samples of theintra-prediction block and the inter-prediction block (356). Videoencoder 200 may then generate a prediction block using the weightedsamples (358). For example, video encoder 200 may calculate values forsamples of the prediction block by executing the following function foreach sample:(wB(x,y)×intraPredPDPC(x,y)+(32−wB(x,y)×interPred(x,y)+16)>>5, where(x,y) represents the position of the sample in the prediction block,intraPredPDPC(x,y) represents the sample at position (x,y) in theintra-prediction block, interPred(x,y) represents the sample at position(x,y) in the inter-prediction block, wB(x,y) represents the firstweight, (32−wB(x,y)) represents the second weight, and ‘>>’ represents abitwise right shift operator.

As an alternative, video encoder 200 may calculate values for samples ofthe prediction block by executing the following function for eachsample:(wL×R_(x-1,y)+wT×R_(x,y-1)−wTL×R_(−1,−1)+(64−wL−wT+wTL)×((intrapred(x,y)+interpred(x,y)+1)>>1)+32)>>6,where R_(x-1,y) represents a left-neighboring reconstructed referencesample to the sample at the position in the current block, R_(x,y-1)represents an above-neighboring reconstructed reference sample to thesample at the position in the current block, wL represents aleft-neighboring weight, wT represents an above-neighboring weight, wTLrepresents a top-left weight, R_(−1,−1) represents a reference sample ata top-left corner of the current block, and ‘>>’ represents a bitwiseright shift operator.

Video encoder 200 may then calculate a residual block for the currentblock (360). To calculate the residual block, video encoder 200 maycalculate a difference between the original, unencoded block and theprediction block for the current block. Video encoder 200 may thentransform and quantize coefficients of the residual block (362). Next,video encoder 200 may scan the quantized transform coefficients of theresidual block (364). During the scan, or following the scan, videoencoder 200 may entropy encode the transform coefficients (366). Forexample, video encoder 200 may encode the transform coefficients usingCAVLC or CABAC. Video encoder 200 may then output the entropy encodeddata of the block (368).

In this manner, the method of FIG. 16 represents an example of a methodof encoding video data including generating an inter-prediction blockfor a current block of video data; generating an intra-prediction blockfor the current block; generating a prediction block for the currentblock, comprising, for each sample of the prediction block: determininga first weight for the sample according to a position of the sample inthe prediction block; determining a second weight for the sampleaccording to the position of the sample in the prediction block;applying the first weight to a sample at the position in theinter-prediction block to generate a weighted inter-prediction sample;applying the second weight to a sample at the position in theintra-prediction block to generate a weighted intra-prediction sample;and calculating a value for the sample at the position in the predictionblock using the weighted inter-prediction sample and the weightedintra-prediction sample; and coding the current block using theprediction block.

FIG. 17 is a flowchart illustrating an example method of decoding videodata according to the techniques of this disclosure. Although describedwith respect to video decoder 300 (FIGS. 1 and 15 ), it should beunderstood that other devices may be configured to perform a methodsimilar to that of FIG. 17 .

Video decoder 300 may receive entropy encoded data for the currentblock, such as entropy encoded prediction information and entropyencoded data for coefficients of a residual block corresponding to thecurrent block (370). Video decoder 300 may entropy decode the entropyencoded data to determine prediction information for the current blockand to reproduce coefficients of the residual block (372). According tothe example of FIG. 17 , the prediction information of the current blockmay indicate that the current block is to be predicted using PDPCaccording to the techniques of this disclosure.

Video decoder 300 may then predict the current block, e.g., using PDPCaccording to the techniques of this disclosure. In particular, videodecoder 300 generates an intra-prediction block for the current block(376) and generates an inter-prediction block for the current block(378). Video decoder 300 may then determine sample position-dependentweights for samples of the intra- and inter-prediction blocks (380).That is, for each sample of the intra- and inter-prediction blocks,video decoder 300 may determine respective weights. In some examples,the sum of the intra-prediction weight and the inter-prediction weightmay be a common value, such as a maximum range value, e.g., 32. Thus,for example, the intra-prediction weight may be referred to as wB andthe inter-prediction weight may be (32−wB).

Video decoder 300 may apply the weights to the respective samples of theintra-prediction block and the inter-prediction block (382). Videodecoder 300 may then generate a prediction block using the weightedsamples (384). For example, video decoder 300 may calculate values forsamples of the prediction block by executing the following function foreach sample:(wB(x,y)×intraPredPDPC(x,y)+(32−wB(x,y)×interPred(x,y)+16)>>5, where(x,y) represents the position of the sample in the prediction block,intraPredPDPC(x,y) represents the sample at position (x,y) in theintra-prediction block, interPred(x,y) represents the sample at position(x,y) in the inter-prediction block, wB(x,y) represents the firstweight, (32−wB(x,y)) represents the second weight, and ‘>>’ represents abitwise right shift operator.

As an alternative, video decoder 300 may calculate values for samples ofthe prediction block by executing the following function for eachsample:(wL×R_(x-1,y)+wT×R_(x,y-1)−wTL×R_(−1,−1)+(64−wL−wT+wTL)×((intrapred(x,y)+interpred(x,y)+1)>>1)+32)>>6,where R_(x-1,y) represents a left-neighboring reconstructed referencesample to the sample at the position in the current block, R_(x,y-1)represents an above-neighboring reconstructed reference sample to thesample at the position in the current block, wL represents aleft-neighboring weight, wT represents an above-neighboring weight, wTLrepresents a top-left weight, R_(−1,−1) represents a reference sample ata top-left corner of the current block, and ‘>>’ represents a bitwiseright shift operator.

Video decoder 300 may then inverse scan the reproduced coefficients(386), to create a block of quantized transform coefficients. Videodecoder 300 may then inverse quantize and inverse transform thetransform coefficients to produce a residual block (388). Video decoder300 may ultimately decode the current block by combining the predictionblock and the residual block (390).

In this manner, the method of FIG. 17 represents an example of a methodof decoding video data including generating an inter-prediction blockfor a current block of video data; generating an intra-prediction blockfor the current block; generating a prediction block for the currentblock, comprising, for each sample of the prediction block: determininga first weight for the sample according to a position of the sample inthe prediction block; determining a second weight for the sampleaccording to the position of the sample in the prediction block;applying the first weight to a sample at the position in theinter-prediction block to generate a weighted inter-prediction sample;applying the second weight to a sample at the position in theintra-prediction block to generate a weighted intra-prediction sample;and calculating a value for the sample at the position in the predictionblock using the weighted inter-prediction sample and the weightedintra-prediction sample; and coding the current block using theprediction block.

It is to be recognized that depending on the example, certain acts orevents of any of the techniques described herein can be performed in adifferent sequence, may be added, merged, or left out altogether (e.g.,not all described acts or events are necessary for the practice of thetechniques). Moreover, in certain examples, acts or events may beperformed concurrently, e.g., through multi-threaded processing,interrupt processing, or multiple processors, rather than sequentially.

In one or more examples, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over as oneor more instructions or code on a computer-readable medium and executedby a hardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable medium.

By way of example, and not limitation, such computer-readable storagemedia can include one or more of RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage, or other magnetic storagedevices, flash memory, or any other medium that can be used to storedesired program code in the form of instructions or data structures andthat can be accessed by a computer. Also, any connection is properlytermed a computer-readable medium. For example, if instructions aretransmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, DSL, orwireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. It should be understood, however,that computer-readable storage media and data storage media do notinclude connections, carrier waves, signals, or other transitory media,but are instead directed to non-transitory, tangible storage media. Diskand disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and Blu-raydisc, where disks usually reproduce data magnetically, while discsreproduce data optically with lasers. Combinations of the above shouldalso be included within the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablegate arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the terms “processor,” “processing circuity,” or“circuit” as used herein may refer to any of the foregoing structures orany other structure suitable for implementation of the techniquesdescribed herein, and may be used inter-changeably where appropriate. Inaddition, in some aspects, the functionality described herein may beprovided within dedicated hardware and/or software circuits configuredfor encoding and decoding, or incorporated in a combined codec. Also,the techniques could be fully implemented in one or more circuits orlogic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a codec hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. A method of coding video data, the methodcomprising: generating an inter-prediction block for a current block ofvideo data; generating an intra-prediction block for the current block;generating a prediction block for the current block, comprising, foreach sample of the prediction block: determining a first weight for thesample according to a position of the sample in the prediction block;determining a second weight for the sample according to the position ofthe sample in the prediction block; applying the first weight to asample at the position in the inter-prediction block to generate aweighted inter-prediction sample; applying the second weight to a sampleat the position in the intra-prediction block to generate a weightedintra-prediction sample; and calculating a value for the sample at theposition in the prediction block using the weighted inter-predictionsample and the weighted intra-prediction sample, including averaging theweighted intra-prediction sample and the weighted inter-predictionsample and blending the average with weighted neighboring reconstructedreference samples of the current block; and coding the current blockusing the prediction block.
 2. The method of claim 1, wherein for eachposition, the sum of the first weight and the second weight is equal toan upper bound range value.
 3. The method of claim 2, wherein the upperbound range value is
 32. 4. The method of claim 1, wherein generatingthe intra-prediction block comprises performing position dependent intraprediction combination (PDPC) following intra-prediction to generate theintra-prediction block.
 5. The method of claim 1, wherein at least twopositions correspond to different respective first weights and differentrespective second weights.
 6. The method of claim 1, wherein generatingthe intra-prediction block comprises generating the intra-predictionblock to have all zero-valued samples.
 7. The method of claim 1, whereincalculating the value for the sample at the position comprises executingthe function(wL×R_(x-1,y)+wT×R_(x,y-1)−wTL×R_(−1,−1)+(64−wL−wT+wTL)×((intrapred(x,y)+interpred(x,y)+1)>>1)+32)>>6,wherein R_(x-1,y) comprises a left-neighboring reconstructed referencesample to the sample at the position in the current block, R_(x,y-1)comprises an above-neighboring reconstructed reference sample to thesample at the position in the current block, wL comprises aleft-neighboring weight, wT comprises an above-neighboring weight, wTLcomprises a top-left weight, R_(−1,−1) comprises a reference sample at atop-left corner of the current block, and ‘>>’ comprises a bitwise rightshift operator.
 8. The method of claim 7, wherein each of wL, WT, andwTL is independent of the position of the sample in the predictionblock.
 9. The method of claim 7, further comprising determining each ofwL, WT, and wTL according to the position of the sample in theprediction block.
 10. The method of claim 7, further comprisingdetermining each of wL, WT, and wTL according to at least one of anintra-prediction mode used to generate the intra-prediction block, aninter-prediction mode used to generate the inter-prediction block, ormotion information used to generate the inter-prediction block.
 11. Themethod of claim 10, further comprising determining each of wL, WT, andwTL according to the position of the sample in the prediction block. 12.The method of claim 1, wherein for each position, the first weightcomprises 1 and the second weight comprises
 1. 13. The method of claim1, wherein coding the current block comprises encoding the currentblock, comprising: generating a residual block representing differencesbetween the current block and the prediction block; and encoding theresidual block.
 14. The method of claim 1, wherein coding the currentblock comprises decoding the current block, comprising: decoding aresidual block representing differences between the current block andthe prediction block; and combining samples of the residual block withsamples of the prediction block to produce a decoded current block. 15.A device for coding video data, the device comprising: a memoryconfigured to store video data; and one or more processors implementedin circuitry and configured to: generate an inter-prediction block for acurrent block of the video data; generate an intra-prediction block forthe current block; generate a prediction block for the current block,wherein to generate the prediction block, the one or more processors areconfigured to, for each sample of the prediction block: determine afirst weight for the sample according to a position of the sample in theprediction block; determine a second weight for the sample according tothe position of the sample in the prediction block; apply the firstweight to a sample at the position in the inter-prediction block togenerate a weighted inter-prediction sample; apply the second weight toa sample at the position in the intra-prediction block to generate aweighted intra-prediction sample; and calculate a value for the sampleat the position in the prediction block using the weightedinter-prediction sample and the weighted intra-prediction sample,wherein to calculate the value for the sample, the one or moreprocessors are configured to average the weighted intra-predictionsample and the weighted inter-prediction sample and blend the averagewith weighted neighboring reconstructed reference samples of the currentblock; and code the current block using the prediction block.
 16. Thedevice of claim 15, wherein for each position, the sum of the firstweight and the second weight is equal to an upper bound range value. 17.The device of claim 16, wherein the upper bound range value is
 32. 18.The device of claim 15, wherein the one or more processors areconfigured to perform position dependent intra prediction combination(PDPC) following intra-prediction to generate the intra-predictionblock.
 19. The device of claim 15, wherein at least two positionscorrespond to different respective first weights and differentrespective second weights.
 20. The device of claim 15, wherein tocalculate the value for the sample, the one or more processors areconfigured to execute the function(wL×R_(x-1,y)+wT×R_(x,y-1)−wTL×R_(−1,−1)+(64−wL−wT+wTL)×((intrapred(x,y)+interpred(x,y)+1)>>1)+32)>>6,wherein R_(x-1,y) comprises a left-neighboring reconstructed referencesample to the sample at the position in the current block, R_(x,y-1)comprises an above-neighboring reconstructed reference sample to thesample at the position in the current block, wL comprises aleft-neighboring weight, wT comprises an above-neighboring weight, wTLcomprises a top-left weight, R_(−1,−1) comprises a reference sample at atop-left corner of the current block, and ‘>>’ comprises a bitwise rightshift operator.
 21. The device of claim 20, wherein each of wL, WT, andwTL is independent of the position of the sample in the predictionblock.
 22. The device of claim 20, wherein the one or more processorsare configured to determine each of wL, WT, and wTL according to theposition of the sample in the prediction block.
 23. The device of claim20, wherein the one or more processors are configured to determine eachof wL, WT, and wTL according to at least one of an intra-prediction modeused to generate the intra-prediction block, an inter-prediction modeused to generate the inter-prediction block, or motion information usedto generate the inter-prediction block.
 24. The device of claim 23,wherein the one or more processors are configured to determine each ofwL, WT, and wTL according to the position of the sample in theprediction block.
 25. The device of claim 15, wherein for each position,the first weight comprises 1 and the second weight comprises
 1. 26. Thedevice of claim 15, wherein the one or more processors are configured toencode the current block, and wherein to encode the current block, theone or more processors are configured to: generate a residual blockrepresenting differences between the current block and the predictionblock; and encode the residual block.
 27. The device of claim 15,wherein the one or more processors are configured to decode the currentblock, and wherein to decode the current block, the one or moreprocessors are configured to: decode a residual block representingdifferences between the current block and the prediction block; andcombine samples of the residual block with samples of the predictionblock to produce a decoded current block.
 28. The device of claim 15,further comprising a display configured to display the video data. 29.The device of claim 15, wherein the device comprises one or more of acamera, a computer, a mobile device, a broadcast receiver device, or aset-top box.
 30. The device of claim 15, wherein the device comprises atleast one of: an integrated circuit; a microprocessor; or a wirelesscommunication device.
 31. A device for decoding video data, the devicecomprising: means for generating an inter-prediction block for a currentblock of video data; means for generating an intra-prediction block forthe current block; means for generating each sample of the predictionblock for the current block, comprising: means for determining a firstweight for the sample according to a position of the sample in theprediction block; means for determining a second weight for the sampleaccording to the position of the sample in the prediction block; meansfor applying the first weight to a sample at the position in theinter-prediction block to generate a weighted inter-prediction sample;means for applying the second weight to a sample at the position in theintra-prediction block to generate a weighted intra-prediction sample;and means for calculating a value for the sample at the position in theprediction block using the weighted inter-prediction sample and theweighted intra-prediction sample, including means for averaging theweighted intra-prediction sample and the weighted inter-predictionsample and blending the average with weighted neighboring reconstructedreference samples of the current block; and means for coding the currentblock using the prediction block.
 32. The device of claim 31, whereinfor each position, the sum of the first weight and the second weight isequal to an upper bound range value.
 33. The device of claim 32, whereinthe upper bound range value is
 32. 34. The device of claim 31, whereinthe means for generating the intra-prediction block comprises means forperforming position dependent intra prediction combination (PDPC)following intra-prediction to generate the intra-prediction block. 35.The device of claim 31, wherein at least two positions correspond todifferent respective first weights and different respective secondweights.
 36. The device of claim 31, wherein the means for coding thecurrent block comprises means for encoding the current block,comprising: means for generating a residual block representingdifferences between the current block and the prediction block; andmeans for encoding the residual block.
 37. The device of claim 31,wherein the means for coding the current block comprises means fordecoding the current block, comprising: means for decoding a residualblock representing differences between the current block and theprediction block; and means for combining samples of the residual blockwith samples of the prediction block to produce a decoded current block.38. A non-transitory computer-readable storage medium having storedthereon instructions that, when executed, cause a processor of a devicefor encoding video data to: generate an inter-prediction block for acurrent block of video data; generate an intra-prediction block for thecurrent block; generate a prediction block for the current block,comprising instructions that cause the processor to, for each sample ofthe prediction block: determine a first weight for the sample accordingto a position of the sample in the prediction block; determine a secondweight for the sample according to the position of the sample in theprediction block; apply the first weight to a sample at the position inthe inter-prediction block to generate a weighted inter-predictionsample; apply the second weight to a sample at the position in theintra-prediction block to generate a weighted intra-prediction sample;and calculate a value for the sample at the position in the predictionblock using the weighted inter-prediction sample and the weightedintra-prediction sample; including instructions that cause the processorto average the weighted intra-prediction sample and the weightedinter-prediction sample and blending the average with weightedneighboring reconstructed reference samples of the current block; andcode the current block using the prediction block.
 39. Thenon-transitory computer-readable storage medium of claim 38, wherein foreach position, the sum of the first weight and the second weight isequal to an upper bound range value.
 40. The non-transitorycomputer-readable storage medium of claim 39, wherein the upper boundrange value is
 32. 41. The non-transitory computer-readable storagemedium of claim 38, wherein the instructions that cause the processor togenerate the intra-prediction block comprise instructions that cause theprocessor to perform position dependent intra prediction combination(PDPC) following intra-prediction to generate the intra-predictionblock.
 42. The non-transitory computer-readable storage medium of claim38, wherein at least two positions correspond to different respectivefirst weights and different respective second weights.
 43. Thenon-transitory computer-readable storage medium of claim 38, wherein theinstructions that cause the processor to calculate the value for thesample include instructions that cause the processor to execute thefunction(wL×R_(x-1,y)+wT×R_(x,y-1)−wTL×R_(−1,−1)+(64−wL−wT+wTL)×((intrapred(x,y)+interpred(x,y)+1)>>1)+32)>>6,wherein R_(x-1,y) comprises a left-neighboring reconstructed referencesample to the sample at the position in the current block, R_(x,y-1)comprises an above-neighboring reconstructed reference sample to thesample at the position in the current block, wL comprises aleft-neighboring weight, wT comprises an above-neighboring weight, wTLcomprises a top-left weight, R_(−1,−1) comprises a reference sample at atop-left corner of the current block, and ‘>>’ comprises a bitwise rightshift operator.